feat: complete v0.2 source and sync management

lib/sync.ts

@@ -0,0 +1,16 @@
+import { db } from "@/lib/db";
+
+export type SyncTrigger = "manual" | "webhook" | "scheduled" | "source-created";
+
+/** Queue one pull per source at a time. Returns true only when a new job was created. */
+export function queuePull(sourceId: number, trigger: SyncTrigger, payload: unknown = {}) {
+  const result = db.prepare(`
+    INSERT INTO sync_jobs(source_id,kind,payload_json,trigger)
+    SELECT ?, 'pull', ?, ?
+    WHERE NOT EXISTS (
+      SELECT 1 FROM sync_jobs
+      WHERE source_id=? AND kind='pull' AND status IN ('queued','running')
+    )
+  `).run(sourceId, JSON.stringify(payload), trigger, sourceId);
+  return result.changes === 1;
+}