feat: add remote device settings portal and Pi hot reload

- add /settings/device portal page and portal device-config GET endpoint
- add portal navigation and client-side device settings editor UI
- hot-reload Account/Car display config after local saves and server syncs
- document portal workflow and Phase 25.5b completion
- add runtime reload tests for account, car, and sync callback

Co-authored-by: Copilot <[email protected]>

app.py

@@ -14,6 +14,14 @@ gps = app_gps.start_gps()
 app_sql.start_logging()
 app_upload.start_uploading()
 app_alerts.start_alerting()
+
+
+def _reload_runtime_device_config():
+    account.reload_runtime_config()
+    car.reload_runtime_config()
+
+
+app_device_sync.register_reload_callback(_reload_runtime_device_config)
 app_device_sync.start_sync()
 
 @app.route('/')
@@ -53,6 +61,7 @@ def api_device_config():
     app_device_config.update_device_config(request.get_json(silent=True), errors)
     if errors:
            return jsonify(error="Invalid device config.", fields=errors), 400
+    _reload_runtime_device_config()
     return jsonify(app_device_config.get_device_config())
 
 @app.route('/api/uplink/status')