Add service health checks and dynamic Apps page

Backend polls each registered service's /health endpoint every 30 s via a
background asyncio task. GET /api/services exposes the live status snapshot.
The Apps page now renders from this endpoint — showing "Unavailable" (dimmed,
non-clickable) when a service is registered but its container is unreachable.

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

backend/app/routers/services.py

@@ -0,0 +1,22 @@
+"""
+GET /api/services — returns health status for all registered feature services.
+Available to any authenticated user so the frontend can drive app visibility.
+"""
+from fastapi import APIRouter, Depends
+
+from app.deps import get_current_user
+from app.models.user import User
+from app.services.service_health import get_all_statuses
+
+router = APIRouter()
+
+
+@router.get("")
+async def list_services(_: User = Depends(get_current_user)) -> list[dict]:
+    """
+    Returns each registered service with its current health status.
+
+    healthy=true  → service responded 200 on its last /health poll
+    healthy=false → unreachable, timed out, or not yet polled
+    """
+    return get_all_statuses()