Add SettingsTab, StatusTab, DataTab and wire up DeviceController

- SettingsTab: chamber ID, master CSV mapping, wafer behavior toggle,
  light/dark mode toggle, Edit CSV Metadata dialog
- StatusTab: connection status, wafer info, activity log (blank until
  Detect Wafer fires)
- DataTab: empty state, ready for parsed data
- HomePage: side rail buttons dispatch device actions and jump to Status
  tab; selectedSideActionIndex defaults to -1 (nothing active on startup)
- DeviceController registered as QML context property in main.py
- LocalSettings: added status persistence fields
- Theme: added subheadingColor and disabledText
- Added serialcomm/ package and backend data/graph modules
- gitignore: added build/, dist/, *.spec

serialcomm/__init__.py

@@ -0,0 +1,6 @@
+"""Serial port communication layer for the temperature-sensing wafer."""
+
+from serialcomm.device_service import DeviceService
+from serialcomm.serial_port import SerialPort, WaferInfo
+
+__all__ = ["DeviceService", "SerialPort", "WaferInfo"]