feat(proxy): implement independent failover queue management

Add a new failover queue system that operates independently from provider
sortIndex, allowing users to configure failover order per app type.

Backend changes:
- Add failover_queue table to schema.rs for persistent storage
- Create dao/failover.rs with CRUD operations for queue management
- Add Tauri commands for queue operations (get, add, remove, reorder, toggle)
- Refactor provider_router.rs select_providers() to use failover queue:
  - Current provider always takes first priority
  - Queue providers ordered by queue_order as fallback
  - Only providers with open circuit breakers are included

Frontend changes:
- Add FailoverQueueItem type to proxy.ts
- Extend failover.ts API with queue management methods
- Add React Query hooks for queue data fetching and mutations
- Create FailoverQueueManager component with drag-and-drop reordering
- Integrate queue management into SettingsPage under "Auto Failover"
- Add i18n translations for zh and en locales

src-tauri/src/commands/failover.rs

@@ -0,0 +1,84 @@
+//! 故障转移队列命令
+//!
+//! 管理代理模式下的故障转移队列
+
+use crate::database::FailoverQueueItem;
+use crate::provider::Provider;
+use crate::store::AppState;
+
+/// 获取故障转移队列
+#[tauri::command]
+pub async fn get_failover_queue(
+    state: tauri::State<'_, AppState>,
+    app_type: String,
+) -> Result<Vec<FailoverQueueItem>, String> {
+    state
+        .db
+        .get_failover_queue(&app_type)
+        .map_err(|e| e.to_string())
+}
+
+/// 获取可添加到故障转移队列的供应商（不在队列中的）
+#[tauri::command]
+pub async fn get_available_providers_for_failover(
+    state: tauri::State<'_, AppState>,
+    app_type: String,
+) -> Result<Vec<Provider>, String> {
+    state
+        .db
+        .get_available_providers_for_failover(&app_type)
+        .map_err(|e| e.to_string())
+}
+
+/// 添加供应商到故障转移队列
+#[tauri::command]
+pub async fn add_to_failover_queue(
+    state: tauri::State<'_, AppState>,
+    app_type: String,
+    provider_id: String,
+) -> Result<(), String> {
+    state
+        .db
+        .add_to_failover_queue(&app_type, &provider_id)
+        .map_err(|e| e.to_string())
+}
+
+/// 从故障转移队列移除供应商
+#[tauri::command]
+pub async fn remove_from_failover_queue(
+    state: tauri::State<'_, AppState>,
+    app_type: String,
+    provider_id: String,
+) -> Result<(), String> {
+    state
+        .db
+        .remove_from_failover_queue(&app_type, &provider_id)
+        .map_err(|e| e.to_string())
+}
+
+/// 重新排序故障转移队列
+#[tauri::command]
+pub async fn reorder_failover_queue(
+    state: tauri::State<'_, AppState>,
+    app_type: String,
+    provider_ids: Vec<String>,
+) -> Result<(), String> {
+    state
+        .db
+        .reorder_failover_queue(&app_type, &provider_ids)
+        .map_err(|e| e.to_string())
+}
+
+/// 设置故障转移队列项的启用状态
+#[tauri::command]
+pub async fn set_failover_item_enabled(
+    state: tauri::State<'_, AppState>,
+    app_type: String,
+    provider_id: String,
+    enabled: bool,
+) -> Result<(), String> {
+    state
+        .db
+        .set_failover_item_enabled(&app_type, &provider_id, enabled)
+        .map_err(|e| e.to_string())
+}

src-tauri/src/commands/mod.rs

@@ -3,6 +3,7 @@
 mod config;
 mod deeplink;
 mod env;
+mod failover;
 mod import_export;
 mod mcp;
 mod misc;
@@ -18,6 +19,7 @@ mod usage;
 pub use config::*;
 pub use deeplink::*;
 pub use env::*;
+pub use failover::*;
 pub use import_export::*;
 pub use mcp::*;
 pub use misc::*;

src-tauri/src/database/dao/failover.rs

@@ -0,0 +1,248 @@
+//! 故障转移队列 DAO
+//!
+//! 管理代理模式下的故障转移队列
+
+use crate::database::{lock_conn, Database};
+use crate::error::AppError;
+use crate::provider::Provider;
+use serde::{Deserialize, Serialize};
+use std::time::{SystemTime, UNIX_EPOCH};
+
+/// 故障转移队列条目
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "camelCase")]
+pub struct FailoverQueueItem {
+    pub provider_id: String,
+    pub provider_name: String,
+    pub queue_order: i32,
+    pub enabled: bool,
+    pub created_at: i64,
+}
+
+impl Database {
+    /// 获取故障转移队列（按 queue_order 排序）
+    pub fn get_failover_queue(&self, app_type: &str) -> Result<Vec<FailoverQueueItem>, AppError> {
+        let conn = lock_conn!(self.conn);
+
+        let mut stmt = conn
+            .prepare(
+                "SELECT fq.provider_id, p.name, fq.queue_order, fq.enabled, fq.created_at
+                 FROM failover_queue fq
+                 JOIN providers p ON fq.provider_id = p.id AND fq.app_type = p.app_type
+                 WHERE fq.app_type = ?1
+                 ORDER BY fq.queue_order ASC",
+            )
+            .map_err(|e| AppError::Database(e.to_string()))?;
+
+        let items = stmt
+            .query_map([app_type], |row| {
+                Ok(FailoverQueueItem {
+                    provider_id: row.get(0)?,
+                    provider_name: row.get(1)?,
+                    queue_order: row.get(2)?,
+                    enabled: row.get(3)?,
+                    created_at: row.get(4)?,
+                })
+            })
+            .map_err(|e| AppError::Database(e.to_string()))?
+            .collect::<Result<Vec<_>, _>>()
+            .map_err(|e| AppError::Database(e.to_string()))?;
+
+        Ok(items)
+    }
+
+    /// 获取故障转移队列中的供应商（完整 Provider 信息，按顺序）
+    pub fn get_failover_providers(&self, app_type: &str) -> Result<Vec<Provider>, AppError> {
+        let queue = self.get_failover_queue(app_type)?;
+        let all_providers = self.get_all_providers(app_type)?;
+
+        let mut result = Vec::new();
+        for item in queue {
+            if item.enabled {
+                if let Some(provider) = all_providers.get(&item.provider_id) {
+                    result.push(provider.clone());
+                }
+            }
+        }
+
+        Ok(result)
+    }
+
+    /// 添加供应商到故障转移队列末尾
+    pub fn add_to_failover_queue(
+        &self,
+        app_type: &str,
+        provider_id: &str,
+    ) -> Result<(), AppError> {
+        let conn = lock_conn!(self.conn);
+
+        // 获取当前最大 queue_order
+        let max_order: i32 = conn
+            .query_row(
+                "SELECT COALESCE(MAX(queue_order), 0) FROM failover_queue WHERE app_type = ?1",
+                [app_type],
+                |row| row.get(0),
+            )
+            .map_err(|e| AppError::Database(e.to_string()))?;
+
+        let now = SystemTime::now()
+            .duration_since(UNIX_EPOCH)
+            .unwrap_or_default()
+            .as_secs() as i64;
+
+        conn.execute(
+            "INSERT OR IGNORE INTO failover_queue (app_type, provider_id, queue_order, enabled, created_at)
+             VALUES (?1, ?2, ?3, 1, ?4)",
+            rusqlite::params![app_type, provider_id, max_order + 1, now],
+        )
+        .map_err(|e| AppError::Database(e.to_string()))?;
+
+        Ok(())
+    }
+
+    /// 从故障转移队列中移除供应商
+    pub fn remove_from_failover_queue(
+        &self,
+        app_type: &str,
+        provider_id: &str,
+    ) -> Result<(), AppError> {
+        let conn = lock_conn!(self.conn);
+
+        // 获取被删除项的 queue_order
+        let removed_order: Option<i32> = conn
+            .query_row(
+                "SELECT queue_order FROM failover_queue WHERE app_type = ?1 AND provider_id = ?2",
+                [app_type, provider_id],
+                |row| row.get(0),
+            )
+            .ok();
+
+        // 删除该项
+        conn.execute(
+            "DELETE FROM failover_queue WHERE app_type = ?1 AND provider_id = ?2",
+            [app_type, provider_id],
+        )
+        .map_err(|e| AppError::Database(e.to_string()))?;
+
+        // 重新排序后面的项（填补空隙）
+        if let Some(order) = removed_order {
+            conn.execute(
+                "UPDATE failover_queue
+                 SET queue_order = queue_order - 1
+                 WHERE app_type = ?1 AND queue_order > ?2",
+                rusqlite::params![app_type, order],
+            )
+            .map_err(|e| AppError::Database(e.to_string()))?;
+        }
+
+        Ok(())
+    }
+
+    /// 重新排序故障转移队列
+    /// provider_ids: 按新顺序排列的 provider_id 列表
+    pub fn reorder_failover_queue(
+        &self,
+        app_type: &str,
+        provider_ids: &[String],
+    ) -> Result<(), AppError> {
+        let conn = lock_conn!(self.conn);
+
+        // 使用事务确保原子性
+        conn.execute("BEGIN TRANSACTION", [])
+            .map_err(|e| AppError::Database(e.to_string()))?;
+
+        let result = (|| {
+            for (index, provider_id) in provider_ids.iter().enumerate() {
+                conn.execute(
+                    "UPDATE failover_queue
+                     SET queue_order = ?3
+                     WHERE app_type = ?1 AND provider_id = ?2",
+                    rusqlite::params![app_type, provider_id, (index + 1) as i32],
+                )
+                .map_err(|e| AppError::Database(e.to_string()))?;
+            }
+            Ok(())
+        })();
+
+        match result {
+            Ok(_) => {
+                conn.execute("COMMIT", [])
+                    .map_err(|e| AppError::Database(e.to_string()))?;
+                Ok(())
+            }
+            Err(e) => {
+                conn.execute("ROLLBACK", []).ok();
+                Err(e)
+            }
+        }
+    }
+
+    /// 设置故障转移队列中供应商的启用状态
+    pub fn set_failover_item_enabled(
+        &self,
+        app_type: &str,
+        provider_id: &str,
+        enabled: bool,
+    ) -> Result<(), AppError> {
+        let conn = lock_conn!(self.conn);
+
+        conn.execute(
+            "UPDATE failover_queue SET enabled = ?3 WHERE app_type = ?1 AND provider_id = ?2",
+            rusqlite::params![app_type, provider_id, enabled],
+        )
+        .map_err(|e| AppError::Database(e.to_string()))?;
+
+        Ok(())
+    }
+
+    /// 清空故障转移队列
+    pub fn clear_failover_queue(&self, app_type: &str) -> Result<(), AppError> {
+        let conn = lock_conn!(self.conn);
+
+        conn.execute(
+            "DELETE FROM failover_queue WHERE app_type = ?1",
+            [app_type],
+        )
+        .map_err(|e| AppError::Database(e.to_string()))?;
+
+        Ok(())
+    }
+
+    /// 检查供应商是否在故障转移队列中
+    pub fn is_in_failover_queue(
+        &self,
+        app_type: &str,
+        provider_id: &str,
+    ) -> Result<bool, AppError> {
+        let conn = lock_conn!(self.conn);
+
+        let count: i32 = conn
+            .query_row(
+                "SELECT COUNT(*) FROM failover_queue WHERE app_type = ?1 AND provider_id = ?2",
+                [app_type, provider_id],
+                |row| row.get(0),
+            )
+            .map_err(|e| AppError::Database(e.to_string()))?;
+
+        Ok(count > 0)
+    }
+
+    /// 获取可添加到故障转移队列的供应商（不在队列中的）
+    pub fn get_available_providers_for_failover(
+        &self,
+        app_type: &str,
+    ) -> Result<Vec<Provider>, AppError> {
+        let all_providers = self.get_all_providers(app_type)?;
+        let queue = self.get_failover_queue(app_type)?;
+
+        let queue_ids: std::collections::HashSet<_> =
+            queue.iter().map(|item| &item.provider_id).collect();
+
+        let available: Vec<Provider> = all_providers
+            .into_values()
+            .filter(|p| !queue_ids.contains(&p.id))
+            .collect();
+
+        Ok(available)
+    }
+}

src-tauri/src/database/dao/mod.rs

@@ -2,6 +2,7 @@
 //!
 //! Database access operations for each domain
 
+pub mod failover;
 pub mod mcp;
 pub mod prompts;
 pub mod providers;
@@ -11,3 +12,5 @@ pub mod skills;
 pub mod stream_check;
 
 // 所有 DAO 方法都通过 Database impl 提供，无需单独导出
+// 导出 FailoverQueueItem 供外部使用
+pub use failover::FailoverQueueItem;

src-tauri/src/database/mod.rs

@@ -31,6 +31,9 @@ mod schema;
 #[cfg(test)]
 mod tests;
 
+// DAO 类型导出供外部使用
+pub use dao::FailoverQueueItem;
+
 use crate::config::get_app_config_dir;
 use crate::error::AppError;
 use rusqlite::Connection;

src-tauri/src/database/schema.rs

@@ -319,6 +319,30 @@ impl Database {
             [],
         );
 
+        // 14. Failover Queue 表 (故障转移队列)
+        conn.execute(
+            "CREATE TABLE IF NOT EXISTS failover_queue (
+                id INTEGER PRIMARY KEY AUTOINCREMENT,
+                app_type TEXT NOT NULL,
+                provider_id TEXT NOT NULL,
+                queue_order INTEGER NOT NULL,
+                enabled INTEGER NOT NULL DEFAULT 1,
+                created_at INTEGER NOT NULL,
+                UNIQUE (app_type, provider_id),
+                FOREIGN KEY (provider_id, app_type) REFERENCES providers(id, app_type) ON DELETE CASCADE
+            )",
+            [],
+        )
+        .map_err(|e| AppError::Database(e.to_string()))?;
+
+        // 为故障转移队列创建索引
+        conn.execute(
+            "CREATE INDEX IF NOT EXISTS idx_failover_queue_order
+             ON failover_queue(app_type, queue_order)",
+            [],
+        )
+        .map_err(|e| AppError::Database(e.to_string()))?;
+
         Ok(())
     }
 

src-tauri/src/lib.rs

@@ -686,6 +686,13 @@ pub fn run() {
             commands::get_circuit_breaker_config,
             commands::update_circuit_breaker_config,
             commands::get_circuit_breaker_stats,
+            // Failover queue management
+            commands::get_failover_queue,
+            commands::get_available_providers_for_failover,
+            commands::add_to_failover_queue,
+            commands::remove_from_failover_queue,
+            commands::reorder_failover_queue,
+            commands::set_failover_item_enabled,
             // Usage statistics
             commands::get_usage_summary,
             commands::get_usage_trends,

src-tauri/src/proxy/provider_router.rs

@@ -28,44 +28,92 @@ impl ProviderRouter {
     }
 
     /// 选择可用的供应商（支持故障转移）
-    /// 返回按优先级排序的可用供应商列表
+    ///
+    /// 返回按优先级排序的可用供应商列表：
+    /// 1. 当前供应商（is_current=true）始终第一位
+    /// 2. 故障转移队列中的其他供应商（按 queue_order 排序）
+    /// 3. 只返回熔断器未打开的供应商
     pub async fn select_providers(&self, app_type: &str) -> Result<Vec<Provider>, AppError> {
-        // 直接获取当前选中的供应商（基于 is_current 字段）
-        let current_id = self
-            .db
-            .get_current_provider(app_type)?
-            .ok_or_else(|| AppError::Config(format!("No current provider for {}", app_type)))?;
+        let mut result = Vec::new();
+        let all_providers = self.db.get_all_providers(app_type)?;
 
-        let providers = self.db.get_all_providers(app_type)?;
-        let provider = providers
-            .get(&current_id)
-            .ok_or_else(|| AppError::Config(format!("Current provider {} not found", current_id)))?
-            .clone();
+        // 1. 当前供应商始终第一位
+        if let Some(current_id) = self.db.get_current_provider(app_type)? {
+            if let Some(current) = all_providers.get(&current_id) {
+                let circuit_key = format!("{}:{}", app_type, current.id);
+                let breaker = self.get_or_create_circuit_breaker(&circuit_key).await;
 
-        log::info!(
-            "[{}] Selected current provider: {} ({})",
-            app_type,
-            provider.name,
-            provider.id
-        );
+                if breaker.allow_request().await {
+                    log::info!(
+                        "[{}] Current provider available: {} ({})",
+                        app_type,
+                        current.name,
+                        current.id
+                    );
+                    result.push(current.clone());
+                } else {
+                    log::warn!(
+                        "[{}] Current provider {} circuit breaker open, checking failover queue",
+                        app_type,
+                        current.name
+                    );
+                }
+            }
+        }
 
-        // 检查熔断器状态
-        let circuit_key = format!("{}:{}", app_type, provider.id);
-        let breaker = self.get_or_create_circuit_breaker(&circuit_key).await;
+        // 2. 获取故障转移队列中的供应商
+        let queue = self.db.get_failover_queue(app_type)?;
 
-        if !breaker.allow_request().await {
-            log::warn!(
-                "Provider {} is unavailable (circuit breaker open)",
-                provider.id
-            );
+        for item in queue {
+            // 跳过已添加的当前供应商
+            if result.iter().any(|p| p.id == item.provider_id) {
+                continue;
+            }
+
+            // 跳过禁用的队列项
+            if !item.enabled {
+                continue;
+            }
+
+            // 获取供应商信息
+            if let Some(provider) = all_providers.get(&item.provider_id) {
+                // 检查熔断器状态
+                let circuit_key = format!("{}:{}", app_type, provider.id);
+                let breaker = self.get_or_create_circuit_breaker(&circuit_key).await;
+
+                if breaker.allow_request().await {
+                    log::info!(
+                        "[{}] Failover provider available: {} ({}) at queue position {}",
+                        app_type,
+                        provider.name,
+                        provider.id,
+                        item.queue_order
+                    );
+                    result.push(provider.clone());
+                } else {
+                    log::debug!(
+                        "[{}] Failover provider {} circuit breaker open, skipping",
+                        app_type,
+                        provider.name
+                    );
+                }
+            }
+        }
+
+        if result.is_empty() {
             return Err(AppError::Config(format!(
-                "Current provider {} is unavailable (circuit breaker open)",
-                provider.name
+                "No available provider for {} (all circuit breakers open or no providers configured)",
+                app_type
             )));
         }
 
-        // 返回单个供应商（保留 Vec 接口以兼容现有代码）
-        Ok(vec![provider])
+        log::info!(
+            "[{}] Failover chain: {} provider(s) available",
+            app_type,
+            result.len()
+        );
+
+        Ok(result)
     }
 
     /// 记录供应商请求结果