Add cron statistics panel for script observability

[Copilot]

No way to get a high-level view of script execution health across many tasks — no totals, no trends, no outliers.

Backend

• back/data/cronLog.ts — New CronLog Sequelize model (SQLite) storing per-execution records: cron_id, cron_name, start_time (Unix seconds), duration (seconds), indexed on both columns
• back/loaders/db.ts — Syncs CronLog table on startup
• back/services/cron.ts — Hooks into status() to persist a CronLog entry whenever a job transitions to idle with last_running_time > 0
• back/services/cronStats.ts — Statistics service with:
  • stats() — task totals (all/enabled/disabled) + today's execution count and avg duration
  • trend() — per-day execution counts for the last 7 days
  • topDuration(5) / topCount(5) — today's slowest and most-frequent tasks with avg/max duration
• back/api/cron.ts — Four new read-only endpoints:
  • GET /crons/stats
  • GET /crons/stats/trend
  • GET /crons/stats/top-duration
  • GET /crons/stats/top-count

Frontend

• src/pages/statistics/index.tsx — New page composed of four modules:
  • Overview stat cards (total/enabled/disabled, today's runs, avg duration)
  • 7-day execution trend — pure SVG line chart, zero new dependencies
  • Top 5 by average duration (avg + max)
  • Top 5 by execution count (count + avg duration)
• Sidebar nav entry, document title mapping, and zh-CN / en-US i18n keys added

Notes

Execution success/failure is not tracked yet — the current shell update_cron call does not propagate an exit code. The schema and service are structured to accommodate that extension without breaking changes.

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Project	Deployment	Actions	Updated (UTC)
qinglong	Ready	Preview, Comment	Apr 25, 2026 7:04am
qinglong-back	Ready	Preview, Comment	Apr 25, 2026 7:04am