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

.gitignore

@@ -28,3 +28,10 @@ qrc_*.cpp
 moc_*.cpp
 *.qmlcache
 *.qmldir.cache
+
+# Build / packaging artifacts
+build/
+dist/
+*.spec
+*.icns
+*.ico