Fix cluster client uptime to show time since last successful connection

- Update connected_at timestamp on each successful connection
- Uptime now resets to 00:00:00 on reconnections as expected

vidai/database.py

@@ -1662,25 +1662,13 @@ def save_cluster_client(client_id: str, token: str, hostname: str, ip_address: s
                 gpu_info = VALUES(gpu_info),
                 available_backends = VALUES(available_backends),
                 connected = 1,
+                connected_at = CURRENT_TIMESTAMP,
                 last_seen = CURRENT_TIMESTAMP
         ''', (client_id, token, hostname, ip_address, weight, gpu_info_json, available_backends_json))
     else:
-        # For SQLite, preserve connected_at if client already exists
-        cursor.execute('SELECT connected_at FROM cluster_clients WHERE client_id = ?', (client_id,))
-        existing = cursor.fetchone()
-
-        if existing and existing['connected_at']:
-            # Update existing client, preserve connected_at
-            cursor.execute('''
-                UPDATE cluster_clients SET
-                    hostname = ?, ip_address = ?, weight = ?, gpu_info = ?, available_backends = ?,
-                    connected = 1, last_seen = CURRENT_TIMESTAMP
-                WHERE client_id = ?
-            ''', (hostname, ip_address, weight, gpu_info_json, available_backends_json, client_id))
-        else:
-            # Insert new client
+        # For SQLite, update connected_at on each successful connection
         cursor.execute('''
-                INSERT INTO cluster_clients
+            INSERT OR REPLACE INTO cluster_clients
             (client_id, token, hostname, ip_address, weight, gpu_info, available_backends, connected, connected_at, last_seen)
             VALUES (?, ?, ?, ?, ?, ?, ?, 1, CURRENT_TIMESTAMP, CURRENT_TIMESTAMP)
         ''', (client_id, token, hostname, ip_address, weight, gpu_info_json, available_backends_json))