Add local SQLite database and sync with Uptime Kuma

Features:
- SQLite database to track monitors and hosts locally
- Uses Uptime Kuma tags to mark monitors as managed by Kuma Strapper
- Sync on startup, before each scan, and on-demand via API
- Shows existing monitors when re-scanning a host

New files:
- backend/services/database.py - SQLite database service
- backend/services/sync.py - Sync service for Uptime Kuma reconciliation

API endpoints:
- POST /api/sync - Full sync with Uptime Kuma
- POST /api/sync/host/<hostname> - Sync specific host
- GET /api/hosts - List tracked hosts
- GET /api/hosts/<hostname>/monitors - Get monitors for host
- GET /api/monitors/tracked - Get all tracked monitors

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app.py

@@ -17,6 +17,8 @@ from services.monitors import (
     parse_docker_containers_from_scan,
 )
 from services.kuma_client import get_kuma_client
+from services.database import get_database
+from services.sync import get_sync_service
 from utils.approval import get_approval_queue, ApprovalStatus
 
 
@@ -90,6 +92,20 @@ def start_scan():
 
     # Start scan in background thread
     def run_scan():
+        # Sync this host's monitors before scanning
+        try:
+            sync = get_sync_service()
+            sync_result = sync.sync_host(hostname)
+            db = get_database()
+            existing_monitors = db.get_monitors_for_hostname(hostname)
+            socketio.emit("host_sync_complete", {
+                "hostname": hostname,
+                "sync_result": sync_result,
+                "existing_monitors": [m.to_dict() for m in existing_monitors],
+            })
+        except Exception as e:
+            print(f"Pre-scan sync failed (non-fatal): {e}")
+
         discovery = get_discovery_service()
 
         def on_progress(cmd_name, status):
@@ -576,6 +592,72 @@ def test_kuma_connection():
         return jsonify({"connected": False, "error": str(e)})
 
 
+# Sync endpoints
+@app.route("/api/sync", methods=["POST"])
+def trigger_sync():
+    """Trigger a full sync with Uptime Kuma."""
+    try:
+        sync = get_sync_service()
+        result = sync.full_sync()
+        return jsonify(result)
+    except Exception as e:
+        return jsonify({"error": str(e)}), 500
+
+
+@app.route("/api/sync/host/<hostname>", methods=["POST"])
+def sync_host(hostname):
+    """Sync monitors for a specific host."""
+    try:
+        sync = get_sync_service()
+        result = sync.sync_host(hostname)
+        return jsonify(result)
+    except Exception as e:
+        return jsonify({"error": str(e)}), 500
+
+
+@app.route("/api/hosts", methods=["GET"])
+def get_hosts():
+    """Get all tracked hosts."""
+    try:
+        db = get_database()
+        hosts = db.get_all_hosts()
+        return jsonify({
+            "hosts": [h.to_dict() for h in hosts],
+            "count": len(hosts)
+        })
+    except Exception as e:
+        return jsonify({"error": str(e)}), 500
+
+
+@app.route("/api/hosts/<hostname>/monitors", methods=["GET"])
+def get_host_monitors(hostname):
+    """Get all tracked monitors for a host."""
+    try:
+        db = get_database()
+        monitors = db.get_monitors_for_hostname(hostname)
+        return jsonify({
+            "hostname": hostname,
+            "monitors": [m.to_dict() for m in monitors],
+            "count": len(monitors)
+        })
+    except Exception as e:
+        return jsonify({"error": str(e)}), 500
+
+
+@app.route("/api/monitors/tracked", methods=["GET"])
+def get_tracked_monitors():
+    """Get all tracked monitors across all hosts."""
+    try:
+        db = get_database()
+        monitors = db.get_all_monitors()
+        return jsonify({
+            "monitors": [m.to_dict() for m in monitors],
+            "count": len(monitors)
+        })
+    except Exception as e:
+        return jsonify({"error": str(e)}), 500
+
+
 # WebSocket events
 @socketio.on("connect")
 def handle_connect():
@@ -587,6 +669,19 @@ def handle_disconnect():
     pass
 
 
+def startup_sync():
+    """Run initial sync with Uptime Kuma on startup."""
+    try:
+        print("Running startup sync with Uptime Kuma...")
+        sync = get_sync_service()
+        result = sync.full_sync()
+        print(f"Startup sync complete: added={result['added']}, updated={result['updated']}, removed={result['removed']}")
+        if result['errors']:
+            print(f"Sync errors: {result['errors']}")
+    except Exception as e:
+        print(f"Startup sync failed (non-fatal): {e}")
+
+
 if __name__ == "__main__":
     # Validate config on startup
     config = get_config()
@@ -600,4 +695,13 @@ if __name__ == "__main__":
         print("Configuration OK")
         print(f"Dev mode: {'enabled' if config.dev_mode else 'disabled'}")
 
+        # Run startup sync in background after short delay
+        def delayed_sync():
+            import time
+            time.sleep(2)  # Wait for app to fully start
+            startup_sync()
+
+        sync_thread = threading.Thread(target=delayed_sync, daemon=True)
+        sync_thread.start()
+
     socketio.run(app, host="0.0.0.0", port=5000, debug=os.environ.get("DEBUG", "false").lower() == "true")