Implement SQLite-based event persistence as specified in sqlite-event-manager.md.
## Changes
### Backend
- **EventStorage** (`src/classes/event_storage.py`): New SQLite storage layer
- Cursor-based pagination with compound cursor `{month_stamp}_{rowid}`
- Avatar filtering (single and pair queries)
- Major/minor event separation
- Cleanup API with `keep_major` and `before_month_stamp` filters
- **EventManager** (`src/classes/event_manager.py`): Refactored to use SQLite
- Delegates to EventStorage for persistence
- Memory fallback mode for testing
- New `get_events_paginated()` method
- **API** (`src/server/main.py`):
- `GET /api/events` - Paginated event retrieval with filtering
- `DELETE /api/events/cleanup` - User-triggered cleanup
### Frontend
- **EventPanel.vue**: Scroll-to-load pagination, dual-person filter UI
- **world.ts**: Event state management with pagination
- **game.ts**: New API client methods
### Testing
- 81 new tests for EventStorage, EventManager, and API
- Added `pytest-asyncio` and `httpx` to requirements.txt
## Known Issues: Save/Load is Currently Broken
After loading a saved game, the following issues occur:
1. **Wrong database used**: API returns events from the startup database instead
of the loaded save's `_events.db` file
2. **Events from wrong time period**: Shows events from year 115 when loaded
save is at year 114
3. **Pagination broken after load**: `has_more` returns `False` despite hundreds
of events in the saved database
4. **Filter functionality broken**: Character selection filter stops working
after loading a game
Root cause: `load_game.py` does not properly switch the EventManager's database
connection to the loaded save's events database.
