feat (volumes): voeg volumes router toe aan backend

Nieuw bestand control/app_volumes.py met Libpod volume operaties:
- GET  /volumes          — lijst alle volumes (optioneel ?filters=key=value)
- POST /volumes          — volume aanmaken (name, driver, labels, driverOpts)
- GET  /volumes/{name}   — details van één volume
- GET  /volumes/{name}/exists — bestaanskontrolle (204 → true, 404 → false)
- DELETE /volumes/{name} — volume verwijderen (?force=true optioneel)
- POST /volumes/prune    — ⚠️ verwijdert alle ongebruikte volumes

Filters: key=value formaat wordt automatisch omgezet naar
{"key":["value"]} JSON dat de Libpod API verwacht.

Containerfile: COPY app_volumes.py toegevoegd.
app.py: init_volumes_router geregistreerd.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

control/app.py

@@ -1,4 +1,5 @@
 from app_images import init_images_router
+from app_volumes import init_volumes_router
 from app_files import init_files_router
 from app_pods import init_pods_router
 from app_containers import init_containers_router, start_stats_poller
@@ -27,6 +28,7 @@ def _systemctl(cmd):
 # --- ROUTERS ---
 # Images API lives in dedicated modules to keep this file from growing further.
 app.include_router(init_images_router(SESSION, PODMAN_API_BASE))
+app.include_router(init_volumes_router(SESSION, PODMAN_API_BASE))
 app.include_router(init_files_router(SESSION, PODMAN_API_BASE, WORKLOADS_DIR))
 app.include_router(init_networks_router(SESSION, PODMAN_API_BASE))
 app.include_router(init_containers_router(