fix: incluir group_id en SELECT de unassignTask

Co-authored-by: aider (openrouter/openai/gpt-5) <aider@aider.chat>

src/tasks/service.ts

@@ -412,7 +412,7 @@ export class TaskService {
 
     const existing = this.dbInstance
       .prepare(`
-        SELECT id, description, due_date, completed, completed_at, display_code
+        SELECT id, description, due_date, group_id, completed, completed_at, display_code
         FROM tasks
         WHERE id = ?
       `)