Release v2.0.0 - Production ready

Version bump:
- Update VERSION to 2.0.0 (from 2.0.0-dev)
- Update pyproject.toml to 2.0.0
- Change development status to Production/Stable

Documentation updates:
- Add Debian package installation instructions (system-wide)
- Add sensor discovery and approval workflow documentation
- Update configuration section with approval workflow
- Update service management for system installation
- Update troubleshooting for system installation
- Update MQTT settings documentation
- Add links to download Debian packages from releases

The application is now production-ready with:
- Systemd integration for automatic service management
- Automatic startup and restart on failure
- Configuration via /etc/sensorpajen/
- Runtime state in /var/lib/sensorpajen/
- Interactive sensor approval workflow
- Automatic configuration reload
- Comprehensive logging via journalctl

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "sensorpajen"
-version = "2.0.0-dev"
+version = "2.0.0"
 description = "Bluetooth temperature sensor monitor for Xiaomi Mijia LYWSD03MMC"
 readme = "README.md"
 requires-python = ">=3.9"
@@ -14,7 +14,7 @@ authors = [
 ]
 keywords = ["bluetooth", "temperature", "sensor", "mqtt", "raspberry-pi"]
 classifiers = [
-    "Development Status :: 4 - Beta",
+    "Development Status :: 5 - Production/Stable",
     "Intended Audience :: Developers",
     "License :: OSI Approved :: MIT License",
     "Programming Language :: Python :: 3",