Add generic AI job queue lifecycle

migrations/001_ai_jobs.up.sql

@@ -18,6 +18,8 @@ CREATE TABLE IF NOT EXISTS ai_jobs (
     scheduled_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
     started_at TIMESTAMPTZ,
     completed_at TIMESTAMPTZ,
+    worker_id TEXT,
+    heartbeat_at TIMESTAMPTZ,
     created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
     updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
     idempotency_key TEXT

migrations/002_ai_jobs_worker_lease.down.sql

@@ -0,0 +1,3 @@
+ALTER TABLE ai_jobs
+    DROP COLUMN IF EXISTS heartbeat_at,
+    DROP COLUMN IF EXISTS worker_id;

migrations/002_ai_jobs_worker_lease.up.sql

@@ -0,0 +1,3 @@
+ALTER TABLE ai_jobs
+    ADD COLUMN IF NOT EXISTS worker_id TEXT,
+    ADD COLUMN IF NOT EXISTS heartbeat_at TIMESTAMPTZ;