Use dependency injection for health status and add health router regression test

backend/app/routers/health.py

@@ -6,16 +6,16 @@ state so monitoring tools and Docker health checks can observe daemon status
 without probing the socket directly.
 """
 
-from fastapi import APIRouter, Request
+from fastapi import APIRouter
 from fastapi.responses import JSONResponse
 
-from app.models.server import ServerStatus
+from app.dependencies import ServerStatusDep
 
 router: APIRouter = APIRouter(prefix="/api", tags=["Health"])
 
 
 @router.get("/health", summary="Application health check")
-async def health_check(request: Request) -> JSONResponse:
+async def health_check(server_status: ServerStatusDep) -> JSONResponse:
     """Return 200 with application and fail2ban status.
 
     HTTP 200 is always returned so Docker health checks do not restart the
@@ -23,15 +23,12 @@ async def health_check(request: Request) -> JSONResponse:
     ``fail2ban`` field in the body indicates the daemon's current state.
 
     Args:
-        request: FastAPI request (used to read cached server status).
+        server_status: Injected cached server status snapshot.
 
     Returns:
         A JSON object with ``{"status": "ok", "fail2ban": "online"|"offline"}``.
     """
-    cached: ServerStatus = getattr(
-        request.app.state, "server_status", ServerStatus(online=False)
-    )
     return JSONResponse(content={
         "status": "ok",
-        "fail2ban": "online" if cached.online else "offline",
+        "fail2ban": "online" if server_status.online else "offline",
     })