feat(model-manager): generated-photo Gallery + device-routing landing

- Gallery view: grid of generated photos from ComfyUI's output/, full-size
  lightbox, and permanent delete (with confirm). Paginated ("Load more").
- Backend: GET /api/gallery, GET /gallery/file (path-guarded image serve),
  DELETE /api/gallery (path-guarded; clear error on permission denial).
- Mount ./output read-write into model-manager so the gallery can delete.
- Device-routing landing at /start: phones -> ComfyUIMini, desktops ->
  the Gallery; ?force=mobile|desktop overrides. Ports come from the new
  /api/ui-config (COMFYUI_PORT / COMFYUIMINI_PORT env).
- Responsive tweaks so the gallery is usable if opened directly on a phone.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docker-compose.yml

@@ -148,11 +148,17 @@ services:
     environment:
       MODELS_DIR: /models
       DATA_DIR: /data
+      OUTPUT_DIR: /output
+      # Ports used by the device-routing landing page (/start)
+      COMFYUI_PORT: "${COMFYUI_PORT:-8188}"
+      COMFYUIMINI_PORT: "${COMFYUIMINI_PORT:-3000}"
 
     volumes:
       # Shared models dir - read-WRITE here so downloads land on the host.
       # ComfyUI mounts the same host folder read-only and picks up new files.
       - ${COMFYUI_HOST_PATH:-.}/models:/models
+      # Generated images - read-WRITE so the gallery can delete photos.
+      - ${SPARKYUI_DATA_PATH:-.}/output:/output
       # Persistent SQLite DB (sources, API keys, download history)
       - ${SPARKYUI_DATA_PATH:-.}/sparkyui-data:/data