feat(monitor): implement code review fixes and real-time WebSocket monitoring

Backend Improvements (11 fixes applied):

Critical Fixes:
- Add lock protection for browser pool access in monitor stats
- Ensure async track_janitor_event across all call sites
- Improve error handling in monitor request tracking (already in place)

Important Fixes:
- Replace fire-and-forget Redis with background persistence worker
- Add time-based expiry for completed requests/errors (5min cleanup)
- Implement input validation for monitor route parameters
- Add 4s timeout to timeline updater to prevent hangs
- Add warning when killing browsers with active requests
- Implement monitor cleanup on shutdown with final persistence
- Document memory estimates with TODO for actual tracking

Frontend Enhancements:

WebSocket Real-time Updates:
- Add WebSocket endpoint at /monitor/ws for live monitoring
- Implement auto-reconnect with exponential backoff (max 5 attempts)
- Add graceful fallback to HTTP polling on WebSocket failure
- Send comprehensive updates every 2 seconds (health, requests, browsers, timeline, events)

UI/UX Improvements:
- Add live connection status indicator with pulsing animation
  - Green "Live" = WebSocket connected
  - Yellow "Connecting..." = Attempting connection
  - Blue "Polling" = Fallback to HTTP polling
  - Red "Disconnected" = Connection failed
- Restore original beautiful styling for all sections
- Improve request table layout with flex-grow for URL column
- Add browser type text labels alongside emojis
- Add flex layout to browser section header

Testing:
- Add test-websocket.py for WebSocket validation
- All 7 integration tests passing successfully

Summary: 563 additions across 6 files

deploy/docker/crawler_pool.py

@@ -61,7 +61,7 @@ async def get_crawler(cfg: BrowserConfig) -> AsyncWebCrawler:
                 # Track promotion in monitor
                 try:
                     from monitor import get_monitor
-                    get_monitor().track_janitor_event("promote", sig, {"count": USAGE_COUNT[sig]})
+                    await get_monitor().track_janitor_event("promote", sig, {"count": USAGE_COUNT[sig]})
                 except:
                     pass
 
@@ -143,7 +143,7 @@ async def janitor():
                     # Track in monitor
                     try:
                         from monitor import get_monitor
-                        get_monitor().track_janitor_event("close_cold", sig, {"idle_seconds": int(idle_time), "ttl": cold_ttl})
+                        await get_monitor().track_janitor_event("close_cold", sig, {"idle_seconds": int(idle_time), "ttl": cold_ttl})
                     except:
                         pass
 
@@ -161,7 +161,7 @@ async def janitor():
                     # Track in monitor
                     try:
                         from monitor import get_monitor
-                        get_monitor().track_janitor_event("close_hot", sig, {"idle_seconds": int(idle_time), "ttl": hot_ttl})
+                        await get_monitor().track_janitor_event("close_hot", sig, {"idle_seconds": int(idle_time), "ttl": hot_ttl})
                     except:
                         pass