Phase 8: Implement Debian package creation (2025-12-27)

- Create debian/ directory structure with all required files:
  - control: Package metadata and dependencies
  - compat: Debhelper compatibility level
  - changelog: Version history
  - rules: Build instructions
  - install: File installation mappings
  - postinst: Post-installation setup (user, venv, setcap)
  - prerm: Pre-removal script (stop service)
  - postrm: Post-removal script (cleanup, preserve config)
  - sensorpajen.service: System-wide systemd unit

- Update config.py to support dual-mode operation:
  - Auto-detects system installation (/opt/sensorpajen)
  - Uses /etc/sensorpajen for config in system mode
  - Falls back to PROJECT_ROOT/config for development

- Update scripts/approve-sensors.sh for system paths:
  - Detects system vs development installation
  - Uses correct venv and config paths

- Create scripts/verify-deb.sh: Automated build and verification

- Create debian/README.md: Comprehensive packaging documentation

Package features:
- System-wide installation to /opt/sensorpajen/
- Configuration in /etc/sensorpajen/ (preserved on upgrade/remove)
- Dedicated sensorpajen system user
- Automatic venv creation with dependencies
- Bluetooth capabilities set automatically
- Service auto-enabled but waits for config before starting
- Dual-mode code supports both system and development installations

debian/sensorpajen.service

@@ -0,0 +1,32 @@
+[Unit]
+Description=Sensorpajen - Bluetooth Temperature Sensor Monitor
+Documentation=https://github.com/yourusername/sensorpajen
+After=network.target bluetooth.target
+Wants=bluetooth.target
+
+[Service]
+Type=simple
+User=sensorpajen
+Group=sensorpajen
+WorkingDirectory=/opt/sensorpajen
+EnvironmentFile=/etc/sensorpajen/sensorpajen.env
+ExecStart=/opt/sensorpajen/venv/bin/python -m sensorpajen.main
+Restart=always
+RestartSec=10
+
+# Bluetooth capabilities require this to be false
+NoNewPrivileges=false
+
+# Logging
+StandardOutput=journal
+StandardError=journal
+SyslogIdentifier=sensorpajen
+
+# Security hardening (where possible with Bluetooth requirements)
+PrivateTmp=true
+ProtectSystem=strict
+ProtectHome=true
+ReadWritePaths=/etc/sensorpajen
+
+[Install]
+WantedBy=multi-user.target