feat(queue): add jobs table + queue helpers and config (ORCH-1)

Persistent SQLite job queue (F-2b): jobs table + idx, atomic claim_next_job,
enqueue/mark/count/requeue/get helpers. New settings max_concurrency
(ORCH_MAX_CONCURRENCY) and queue_poll_interval (ORCH_QUEUE_POLL_INTERVAL).

src/config.py

@@ -30,6 +30,12 @@ class Settings(BaseSettings):
     # DB
     db_path: str = "/app/data/orchestrator.db"
 
+    # ORCH-1 (F-2b): persistent job queue / background worker.
+    # max_concurrency  -> max agent jobs running in parallel (env ORCH_MAX_CONCURRENCY)
+    # queue_poll_interval -> worker loop poll seconds (env ORCH_QUEUE_POLL_INTERVAL)
+    max_concurrency: int = 1
+    queue_poll_interval: float = 2.0
+
 
     # Telegram notifications
     telegram_bot_token: str = ""