Add in-app settings menu and fix settings API

Move WiFi and device name configuration into a modal menu, reuse existing settings endpoints, and harden settings serialization and startup for MicroPython.

src/controllers/settings.py

@@ -9,7 +9,9 @@ settings = Settings()
 @controller.get('')
 async def get_settings(request):
     """Get all settings."""
-    return json.dumps(dict(settings)), 200, {'Content-Type': 'application/json'}
+    # Settings is already a dict subclass; avoid dict() wrapper which can
+    # trigger MicroPython's "dict update sequence has wrong length" quirk.
+    return json.dumps(settings), 200, {'Content-Type': 'application/json'}
 
 @controller.get('/wifi/station')
 async def get_station_status(request):