feat: add job runs chart and scrollable reading lists on dashboard

- Add multi-line chart showing job runs over time by type (scan,
  rebuild, thumbnails, other) with the same day/week/month toggle
- Limit currently reading and recently read lists to 3 visible items
  with a scrollbar for overflow
- Fix NUMERIC→BIGINT cast for SUM/COALESCE in jobs SQL queries

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

apps/backoffice/lib/i18n/en.ts

@@ -71,6 +71,11 @@ const en: Record<TranslationKey, string> = {
   "dashboard.byFormat": "By format",
   "dashboard.byLibrary": "By library",
   "dashboard.booksAdded": "Books added",
+  "dashboard.jobsOverTime": "Job runs",
+  "dashboard.jobScan": "Scan",
+  "dashboard.jobRebuild": "Rebuild",
+  "dashboard.jobThumbnail": "Thumbnails",
+  "dashboard.jobOther": "Other",
   "dashboard.periodDay": "Day",
   "dashboard.periodWeek": "Week",
   "dashboard.periodMonth": "Month",