feat(admin): observability — job history, live "now analyzing", durations & metrics

Crawler + analysis admin dashboards gain a Live / History / Metrics
segmented view.

History: searchable, filterable, paginated job log per subsystem
(crawler_jobs across all states/kinds; page_analysis terminal outcomes),
with inline dead-job requeue and a Duration column.

Live: enrich analysis SSE events with manga title + chapter number and add
a sticky "Now analyzing" banner that jumps to and highlights the page.

Metrics: new durable crawl_metrics table (migration 0028) timing every
crawl op (manga list walk, manga detail, cover, whole chapter; per-page
derived from chapter) plus page_analysis.duration_ms for analysis. New
endpoints serve per-type average durations + success rates and a recent-ops
log; a cron reaper (CRAWL_METRICS_RETENTION_DAYS) bounds growth.

Tested: repo + API integration tests, vitest for the API client and
fmtDuration, and Playwright for the History/Metrics tabs.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/package.json

@@ -1,6 +1,6 @@
 {
   "name": "mangalord-frontend",
-  "version": "0.82.0",
+  "version": "0.84.0",
   "private": true,
   "type": "module",
   "scripts": {