Refactor response handling and health check endpoints

- Enhance response model with additional fields and validation
- Update health and server router implementations
- Improve frontend type definitions and API integration
- Clean up documentation

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

backend/app/routers/health.py

@@ -10,11 +10,12 @@ from fastapi import APIRouter, status
 from fastapi.responses import JSONResponse
 
 from app.dependencies import ServerStatusDep
+from app.models.response import HealthResponse
 
 router: APIRouter = APIRouter(prefix="/api/v1/health", tags=["Health"])
 
 
-@router.get("", summary="Application health check")
+@router.get("", summary="Application health check", response_model=HealthResponse)
 async def health_check(server_status: ServerStatusDep) -> JSONResponse:
     """Return application and fail2ban status.
 
@@ -27,17 +28,16 @@ async def health_check(server_status: ServerStatusDep) -> JSONResponse:
         server_status: Injected cached server status snapshot.
 
     Returns:
-        HTTP 200 with ``{"status": "ok", "fail2ban": "online"}`` if healthy,
-        or HTTP 503 with ``{"status": "unavailable", "fail2ban": "offline"}``
-        if fail2ban is unreachable.
+        HTTP 200 with :class:`~app.models.response.HealthResponse` when healthy,
+        HTTP 503 with :class:`~app.models.response.HealthResponse` when fail2ban is offline.
     """
     if not server_status.online:
         return JSONResponse(
             status_code=status.HTTP_503_SERVICE_UNAVAILABLE,
-            content={"status": "unavailable", "fail2ban": "offline"},
+            content=HealthResponse(status="unavailable", fail2ban="offline").model_dump(),
         )
 
     return JSONResponse(
         status_code=status.HTTP_200_OK,
-        content={"status": "ok", "fail2ban": "online"},
+        content=HealthResponse(status="ok", fail2ban="online").model_dump(),
     )