Stazioni: camera_url e camera_source, GET /api/stations/by-code/{code} (#72)

Migrazione 020 con le due colonne su stations, campi in modello, schemi e
servizio (validatore http(s) come vision_worker_url), nuova route by-code
dichiarata prima di /{station_id}. Test di migrazione su e giu e di API.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/backend/api/routers/stations.py

@@ -67,6 +67,21 @@ async def create_new_station(
 # The int-typed station_id param already guards against "by-code" being
 # matched as a station id, but keeping the explicit order avoids surprises
 # during refactors (e.g. if someone regroups handlers by HTTP method).
+@router.get("/by-code/{code}", response_model=StationResponse)
+async def get_station_by_code(
+    code: str,
+    admin: User = Depends(require_admin_user),
+    db: AsyncSession = Depends(get_db),
+):
+    """Get a station by its code (admin only, like GET /{station_id}) (#72)."""
+    station = await station_service.get_station_by_code(db, code)
+    if station is None:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND, detail="Station not found",
+        )
+    return StationResponse.model_validate(station)
+
+
 @router.get("/by-code/{code}/recipes", response_model=list[RecipeSummary])
 async def list_recipes_by_station_code(
     code: str,