refactor: replace issues backend with milestone tasks

app/api/routers/monitor.py

@@ -18,7 +18,7 @@ from app.models.monitor import (
     ServerHandshakeNonce,
 )
 from app.services.monitoring import (
-    get_issue_stats_cached,
+    get_task_stats_cached,
     get_provider_usage_view,
     get_server_states_view,
     test_provider_connection,
@@ -66,7 +66,7 @@ def monitor_public_key():
 @router.get('/public/overview')
 def public_overview(db: Session = Depends(get_db)):
     return {
-        'issues': get_issue_stats_cached(db, ttl_seconds=1800),
+        'tasks': get_task_stats_cached(db, ttl_seconds=1800),
         'providers': get_provider_usage_view(db),
         'servers': get_server_states_view(db, offline_after_minutes=7),
         'generated_at': datetime.now(timezone.utc).isoformat(),