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>

USAGE.md

@@ -29,8 +29,8 @@ source venv/bin/activate
 # Run interactive scan
 rf-mapper
 
-# Start web interface
-rf-mapper web
+# Start web server
+rf-mapper start
 ```
 
 ## CLI Commands
@@ -74,23 +74,35 @@ rf-mapper analyze
 rf-mapper list
 ```
 
-### Web Interface
+### Web Server
 
 ```bash
-# Start web server (default: http://0.0.0.0:5000)
-rf-mapper web
+# Start web server (background daemon)
+rf-mapper start
+
+# Start in foreground (for debugging)
+rf-mapper start --foreground
 
 # Custom host/port
-rf-mapper web -H 127.0.0.1 -p 8080
+rf-mapper start -H 127.0.0.1 -p 8080
 
-# Debug mode
-rf-mapper web --debug
+# With debug mode
+rf-mapper start --foreground --debug
 
 # With request profiling
-rf-mapper web --profile-requests
+rf-mapper start --profile-requests
 
 # With request logging
-rf-mapper web --log-requests
+rf-mapper start --log-requests
+
+# Stop the server
+rf-mapper stop
+
+# Restart the server
+rf-mapper restart
+
+# Check server status
+rf-mapper status
 ```
 
 ### Configuration