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]>

server/README.md

@@ -65,6 +65,10 @@ so a permissive origin can't be used to steal a logged-in session.
    docker compose ps
    curl http://localhost:8098/health
    ```
+5. Sign in to the remote portal and open `/settings/device` to edit the synced
+   owner/car/device/avatar values for the configured `DEVICE_NAME`. If the Pi
+   has local **Sync with server** enabled, those values hot-reload into the
+   running Pi UI after the next successful sync.
 
 ### Upgrading an existing unraid deployment
 
@@ -80,7 +84,10 @@ docker compose up -d --build
 
 Phase 25.5a adds the device identity sync columns (`owner_name`, `car_model`,
 `device_name`, `avatar_path`, `config_version`, `config_updated_at`) used by the
-Pi/server config sync flow.
+Pi/server config sync flow. The browser portal page at `/settings/device` edits
+those values; the Pi applies them on its next successful sync when local
+**Sync with server** is enabled, and Phase 25.5b now hot-reloads the in-process
+UI fields instead of requiring an app restart.
 
 ## Registering a device and getting an API key