feat(api): add WebUI API server with built frontend

- Add FastAPI server with WebSocket support for real-time logs
- Add crawler management API endpoints (start/stop/status)
- Add data browsing API endpoints (list files, preview, download)
- Include pre-built WebUI assets for serving frontend

API endpoints:
- POST /api/crawler/start - Start crawler task
- POST /api/crawler/stop - Stop crawler task
- GET /api/crawler/status - Get crawler status
- WS /api/ws/logs - Real-time log streaming
- GET /api/data/files - List data files
- GET /api/data/stats - Get data statistics

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitignore

@@ -178,4 +178,4 @@ docs/.vitepress/cache
 agent_zone
 debug_tools
 
-database/*.db
+database/*.db