feat(monitor): add real-time monitoring dashboard with Redis persistence

Complete observability solution for production deployments with terminal-style UI.

**Backend Implementation:**
- `monitor.py`: Stats manager tracking requests, browsers, errors, timeline data
- `monitor_routes.py`: REST API endpoints for all monitor functionality
  - GET /monitor/health - System health snapshot
  - GET /monitor/requests - Active & completed requests
  - GET /monitor/browsers - Browser pool details
  - GET /monitor/endpoints/stats - Aggregated endpoint analytics
  - GET /monitor/timeline - Time-series data (memory, requests, browsers)
  - GET /monitor/logs/{janitor,errors} - Event logs
  - POST /monitor/actions/{cleanup,kill_browser,restart_browser} - Control actions
  - POST /monitor/stats/reset - Reset counters
- Redis persistence for endpoint stats (survives restart)
- Timeline tracking (5min window, 5s resolution, 60 data points)

**Frontend Dashboard** (`/dashboard`):
- **System Health Bar**: CPU%, Memory%, Network I/O, Uptime
- **Pool Status**: Live counts (permanent/hot/cold browsers + memory)
- **Live Activity Tabs**:
  - Requests: Active (realtime) + recent completed (last 100)
  - Browsers: Detailed table with actions (kill/restart)
  - Janitor: Cleanup event log with timestamps
  - Errors: Recent errors with stack traces
- **Endpoint Analytics**: Count, avg latency, success%, pool hit%
- **Resource Timeline**: SVG charts (memory/requests/browsers) with terminal aesthetics
- **Control Actions**: Force cleanup, restart permanent, reset stats
- **Auto-refresh**: 5s polling (toggleable)

**Integration:**
- Janitor events tracked (close_cold, close_hot, promote)
- Crawler pool promotion events logged
- Timeline updater background task (5s interval)
- Lifespan hooks for monitor initialization

**UI Design:**
- Terminal vibe matching Crawl4AI theme
- Dark background, cyan/pink accents, monospace font
- Neon glow effects on charts
- Responsive layout, hover interactions
- Cross-navigation: Playground ↔ Monitor

**Key Features:**
- Zero-config: Works out of the box with existing Redis
- Real-time visibility into pool efficiency
- Manual browser management (kill/restart)
- Historical data persistence
- DevOps-friendly UX

Routes:
- API: `/monitor/*` (backend endpoints)
- UI: `/dashboard` (static HTML)

deploy/docker/crawler_pool.py

@@ -57,6 +57,14 @@ async def get_crawler(cfg: BrowserConfig) -> AsyncWebCrawler:
             if USAGE_COUNT[sig] >= 3:
                 logger.info(f"⬆️  Promoting to hot pool (sig={sig[:8]}, count={USAGE_COUNT[sig]})")
                 HOT_POOL[sig] = COLD_POOL.pop(sig)
+
+                # Track promotion in monitor
+                try:
+                    from monitor import get_monitor
+                    get_monitor().track_janitor_event("promote", sig, {"count": USAGE_COUNT[sig]})
+                except:
+                    pass
+
                 return HOT_POOL[sig]
 
             logger.info(f"❄️  Using cold pool browser (sig={sig[:8]})")
@@ -124,23 +132,39 @@ async def janitor():
             # Clean cold pool
             for sig in list(COLD_POOL.keys()):
                 if now - LAST_USED.get(sig, now) > cold_ttl:
-                    logger.info(f"🧹 Closing cold browser (sig={sig[:8]}, idle={now - LAST_USED[sig]:.0f}s)")
+                    idle_time = now - LAST_USED[sig]
+                    logger.info(f"🧹 Closing cold browser (sig={sig[:8]}, idle={idle_time:.0f}s)")
                     with suppress(Exception):
                         await COLD_POOL[sig].close()
                     COLD_POOL.pop(sig, None)
                     LAST_USED.pop(sig, None)
                     USAGE_COUNT.pop(sig, None)
 
+                    # 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})
+                    except:
+                        pass
+
             # Clean hot pool (more conservative)
             for sig in list(HOT_POOL.keys()):
                 if now - LAST_USED.get(sig, now) > hot_ttl:
-                    logger.info(f"🧹 Closing hot browser (sig={sig[:8]}, idle={now - LAST_USED[sig]:.0f}s)")
+                    idle_time = now - LAST_USED[sig]
+                    logger.info(f"🧹 Closing hot browser (sig={sig[:8]}, idle={idle_time:.0f}s)")
                     with suppress(Exception):
                         await HOT_POOL[sig].close()
                     HOT_POOL.pop(sig, None)
                     LAST_USED.pop(sig, None)
                     USAGE_COUNT.pop(sig, None)
 
+                    # 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})
+                    except:
+                        pass
+
             # Log pool stats
             if mem_pct > 60:
                 logger.info(f"📊 Pool: hot={len(HOT_POOL)}, cold={len(COLD_POOL)}, mem={mem_pct:.1f}%")