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

main.py

@@ -5,6 +5,8 @@ from PySide6.QtQml import QQmlApplicationEngine
 from PySide6.QtQuickControls2 import QQuickStyle
 from PySide6.QtWidgets import QApplication
 
+from backend.device_controller import DeviceController
+from backend.local_settings import LocalSettings
 from backend.local_settings_model import LocalSettingsModel
 from backend.file_browser import FileBrowser
 
@@ -26,6 +28,12 @@ if __name__ == "__main__":
     engine.rootContext().setContextProperty("settingsModel", settings_model)
     engine.rootContext().setContextProperty("file_browser", select_file_dialog_model)
 
+    # ===== Device Controller (serial comm) =====
+    data_dir = str(settings_model._data_dir)
+    raw_settings = LocalSettings.read_settings(data_dir)
+    device_controller = DeviceController(raw_settings, data_dir)
+    engine.rootContext().setContextProperty("deviceController", device_controller)
+
     # ===== QML Startup =====
     engine.addImportPath(Path(__file__).parent)
     engine.loadFromModule("ISC", "Main")