Add SettingsTab, StatusTab, DataTab and wire up DeviceController

- SettingsTab: chamber ID, master CSV mapping (families A-Z), wafer
  behavior toggle, light/dark mode toggle, Edit CSV Metadata dialog
- StatusTab: connection status card, wafer info, activity log (blank
  until Detect Wafer fires from the side rail)
- DataTab: empty state, ready for parsed data
- HomePage: side rail buttons dispatch device actions and jump to
  Status tab; selectedSideActionIndex defaults to -1 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: restore clean version

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"]