feat: add Home Assistant integration and improve CLI/UI

Home Assistant Integration:
- New homeassistant.py module with webhook support
- Webhooks for scan results, new devices, and device departures
- Absence detection with configurable timeout
- Documentation in docs/HOME_ASSISTANT.md

CLI Improvements:
- Replace 'web' command with start/stop/restart/status
- Background daemon mode with PID file management
- Foreground mode for debugging (--foreground)

Web UI Enhancements:
- Improved device list styling and layout
- Better floor assignment UI
- Enhanced map visualization

Documentation:
- Add CHANGELOG.md
- Add docs/API.md with full endpoint reference
- Add docs/CHEATSHEET.md for quick reference
- Update project documentation

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

PROJECT.md

@@ -31,6 +31,7 @@ Understanding the RF environment around you is useful for:
 - **Historical Database** - SQLite storage for device history, RSSI time-series, statistics
 - **Auto-scan** - Scheduled background scanning
 - **Data Export** - JSON scan history with timestamps
+- **Home Assistant Integration** - Webhook-based presence tracking, new device alerts, departure notifications
 
 ## Architecture
 
@@ -64,6 +65,14 @@ Understanding the RF environment around you is useful for:
 │  │    iw    │  │  bleak   │  │  SQLite  │                   │
 │  │  (WiFi)  │  │  (BLE)   │  │(History) │                   │
 │  └──────────┘  └──────────┘  └──────────┘                   │
+└─────────────────────────┬───────────────────────────────────┘
+                          │ Webhooks
+┌─────────────────────────┴───────────────────────────────────┐
+│                    Home Assistant                            │
+│  ┌──────────────┐  ┌──────────────┐  ┌──────────────┐       │
+│  │ Scan Results │  │ New Device   │  │ Device Gone  │       │
+│  │   Webhook    │  │   Webhook    │  │   Webhook    │       │
+│  └──────────────┘  └──────────────┘  └──────────────┘       │
 └─────────────────────────────────────────────────────────────┘
 ```
 
@@ -81,6 +90,7 @@ Understanding the RF environment around you is useful for:
 - PyYAML - Configuration
 - dataclasses - Data structures
 - bleak - BLE scanning with RSSI
+- requests - HTTP client for webhooks
 
 ### Frontend
 - Leaflet.js - 2D maps
@@ -99,8 +109,11 @@ pip install -e .
 ## Quick Start
 
 ```bash
-# Start web interface
-rf-mapper web
+# Start web server (background)
+rf-mapper start
+
+# Check status
+rf-mapper status
 
 # CLI scan
 rf-mapper scan
@@ -126,6 +139,14 @@ building:
   enabled: true
   floors: 12
   current_floor: 11
+
+home_assistant:
+  enabled: true
+  url: http://192.168.129.10:8123
+  webhook_scan: rf_mapper_scan
+  webhook_new_device: rf_mapper_new_device
+  webhook_device_gone: rf_mapper_device_gone
+  device_timeout_minutes: 5
 ```
 
 ## Documentation