Standardize API response envelopes: use items for collection responses and update tests

backend/app/services/config_service.py

@@ -218,7 +218,7 @@ async def list_jail_configs(socket_path: str) -> JailConfigListResponse:
     )
 
     if not jail_names:
-        return JailConfigListResponse(jails=[], total=0)
+        return JailConfigListResponse(items=[], total=0)
 
     responses: list[JailConfigResponse] = await asyncio.gather(
         *[get_jail_config(socket_path, name) for name in jail_names],
@@ -227,7 +227,7 @@ async def list_jail_configs(socket_path: str) -> JailConfigListResponse:
 
     jails = [r.jail for r in responses]
     log.info("jail_configs_listed", count=len(jails))
-    return JailConfigListResponse(jails=jails, total=len(jails))
+    return JailConfigListResponse(items=jails, total=len(jails))
 
 
 # ---------------------------------------------------------------------------

backend/app/services/jail_config_service.py

@@ -311,7 +311,7 @@ async def list_inactive_jails(
         active=len(active_names),
         inactive=len(inactive),
     )
-    return InactiveJailListResponse(jails=inactive, total=len(inactive))
+    return InactiveJailListResponse(items=inactive, total=len(inactive))
 
 
 async def activate_jail(