fix(i18n): update apiFormatOpenAIChat label to mention proxy requirement

Change label from "Requires conversion" to "Requires proxy" for clarity:
- zh: "需转换" → "需开启代理"
- en: "Requires conversion" → "Requires proxy"
- ja: "変換が必要" → "プロキシが必要"

src/i18n/locales/en.json

@@ -475,7 +475,7 @@
     "apiFormat": "API Format",
     "apiFormatHint": "Select the input format for the provider's API",
     "apiFormatAnthropic": "Anthropic Messages (Native)",
-    "apiFormatOpenAIChat": "OpenAI Chat Completions (Requires conversion)",
+    "apiFormatOpenAIChat": "OpenAI Chat Completions (Requires proxy)",
     "anthropicDefaultHaikuModel": "Default Haiku Model",
     "anthropicDefaultSonnetModel": "Default Sonnet Model",
     "anthropicDefaultOpusModel": "Default Opus Model",

src/i18n/locales/ja.json

@@ -475,7 +475,7 @@
     "apiFormat": "API フォーマット",
     "apiFormatHint": "プロバイダー API の入力フォーマットを選択",
     "apiFormatAnthropic": "Anthropic Messages（ネイティブ）",
-    "apiFormatOpenAIChat": "OpenAI Chat Completions（変換が必要）",
+    "apiFormatOpenAIChat": "OpenAI Chat Completions（プロキシが必要）",
     "anthropicDefaultHaikuModel": "既定 Haiku モデル",
     "anthropicDefaultSonnetModel": "既定 Sonnet モデル",
     "anthropicDefaultOpusModel": "既定 Opus モデル",

src/i18n/locales/zh.json

@@ -475,7 +475,7 @@
     "apiFormat": "API 格式",
     "apiFormatHint": "选择供应商 API 的输入格式",
     "apiFormatAnthropic": "Anthropic Messages (原生)",
-    "apiFormatOpenAIChat": "OpenAI Chat Completions (需转换)",
+    "apiFormatOpenAIChat": "OpenAI Chat Completions (需开启代理)",
     "anthropicDefaultHaikuModel": "Haiku 默认模型",
     "anthropicDefaultSonnetModel": "Sonnet 默认模型",
     "anthropicDefaultOpusModel": "Opus 默认模型",