feat: agregar columna metadata a response_queue

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

src/db.ts

@@ -82,6 +82,7 @@ export function initializeDatabase(instance: Database) {
       status TEXT NOT NULL DEFAULT 'queued' CHECK (status IN ('queued','processing','sent','failed')),
       attempts INTEGER NOT NULL DEFAULT 0,
       last_error TEXT NULL,
+      metadata TEXT NULL,
       created_at TEXT DEFAULT (strftime('%Y-%m-%d %H:%M:%f', 'now')),
       updated_at TEXT DEFAULT (strftime('%Y-%m-%d %H:%M:%f', 'now'))
     );