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>

CLAUDE.md

@@ -15,7 +15,9 @@ src/rf_mapper/
 ├── __main__.py      # CLI entry point and argument parsing
 ├── scanner.py       # WiFi/Bluetooth scanning (WifiNetwork, BluetoothDevice dataclasses)
 ├── config.py        # Configuration management (Config, BuildingConfig, etc.)
+├── database.py      # SQLite database for device history and tracking
 ├── distance.py      # RSSI to distance estimation
+├── homeassistant.py # Home Assistant webhook integration
 ├── oui.py           # MAC address manufacturer lookup
 ├── bluetooth_*.py   # Bluetooth device identification and classification
 ├── visualize.py     # ASCII radar and chart generation
@@ -35,18 +37,23 @@ src/rf_mapper/
 | Modify data model | `src/rf_mapper/scanner.py`, `config.py` |
 | Change web UI | `web/templates/index.html`, `static/js/app.js`, `static/css/style.css` |
 | Add configuration | `src/rf_mapper/config.py`, `config.yaml` |
+| Home Assistant integration | `src/rf_mapper/homeassistant.py`, `docs/HOME_ASSISTANT.md` |
 
 ## Running
 
 ```bash
 source venv/bin/activate
-rf-mapper web          # Web interface at http://localhost:5000
+rf-mapper start        # Start web server (background)
+rf-mapper status       # Check if running
+rf-mapper stop         # Stop server
 rf-mapper scan -l room # CLI scan
 rf-mapper --help       # All commands
 ```
 
 ## Tech Stack
 
-- Python 3.10+, Flask, PyYAML
+- Python 3.10+, Flask, PyYAML, requests
 - Leaflet.js (2D maps), MapLibre GL JS (3D maps)
-- Linux tools: `iw`, `hcitool`, `bluetoothctl`
+- Linux tools: `iw`, bleak (BLE via D-Bus)
+- SQLite for device history
+- Home Assistant webhooks for integration