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/main.py

@@ -1,11 +1,33 @@
+import asyncio
+from contextlib import asynccontextmanager
+
 from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 
 from app.core.config import settings
-from app.routers import admin, auth, categories_proxy, documents_proxy, profile, users
+from app.routers import admin, auth, categories_proxy, documents_proxy, profile, services, users
 from app.routers import settings as settings_router
+from app.services.service_health import check_all, health_check_loop, register_services
 
-app = FastAPI(title=settings.PROJECT_NAME, version="0.1.0")
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    register_services(
+        doc_service_url=settings.DOC_SERVICE_URL,
+        ai_service_url=settings.AI_SERVICE_URL,
+    )
+    # Run an initial check immediately so the first API response is accurate
+    await check_all()
+    task = asyncio.create_task(health_check_loop())
+    yield
+    task.cancel()
+    try:
+        await task
+    except asyncio.CancelledError:
+        pass
+
+
+app = FastAPI(title=settings.PROJECT_NAME, version="0.1.0", lifespan=lifespan)
 
 app.add_middleware(
     CORSMiddleware,
@@ -20,6 +42,7 @@ app.include_router(users.router, prefix="/api/users", tags=["users"])
 app.include_router(profile.router, prefix="/api/profile", tags=["profile"])
 app.include_router(admin.router, prefix="/api/admin", tags=["admin"])
 app.include_router(settings_router.router, prefix="/api/settings", tags=["settings"])
+app.include_router(services.router, prefix="/api/services", tags=["services"])
 # categories_proxy MUST be registered before documents_proxy —
 # otherwise /api/documents/{path:path} swallows /api/documents/categories/*
 app.include_router(