feat: scheduler live status — endpoint + UI polling every 15s

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

main.py

@@ -73,6 +73,26 @@ async def shutdown():
     _scheduler.shutdown(wait=False)
 
 
+@app.get("/api/scheduler/status")
+async def scheduler_status():
+    from fastapi.responses import JSONResponse
+    from app.database import get_connection
+    job = _scheduler.get_job("wa_sync_recientes")
+    next_run = job.next_run_time.isoformat() if job and job.next_run_time else None
+    conn = get_connection()
+    row = conn.execute(
+        "SELECT created_at, total_procesados, total_errores, origen "
+        "FROM sync_wa_log WHERE origen='scheduler' ORDER BY id DESC LIMIT 1"
+    ).fetchone()
+    conn.close()
+    return JSONResponse({
+        "running": _scheduler.running,
+        "job_exists": job is not None,
+        "next_run": next_run,
+        "ultimo_log": dict(row) if row else None,
+    })
+
+
 @app.get("/")
 async def root():
     return RedirectResponse(url="/dashboard")