Remove Jinja2 template fallback (1249 lines) — /admin/performance now serves
Vue SPA exclusively via send_from_directory.
Backend:
- Add _SLOW_QUERY_WAITING counter with get_slow_query_waiting_count()
- Record slow-path latency in read_sql_df_slow/iter via record_query_latency()
- Extend metrics_history schema with slow_query_active, slow_query_waiting,
worker_rss_bytes columns + ALTER TABLE migration for existing DBs
- Add cleanup_archive_logs() with configurable ARCHIVE_LOG_DIR/KEEP_COUNT
- Integrate archive cleanup into MetricsHistoryCollector 50-min cycle
Frontend:
- Add slow_query_active and slow_query_waiting StatCards to connection pool
- Add slow_query_active trend line to pool trend chart
- Add Worker memory (RSS MB) trend chart with preprocessing
- Update modernization gate check path to frontend style.css
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>