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/api.ts

@@ -570,6 +570,14 @@ export type MonthlyReading = {
   books_read: number;
 };
 
+export type JobTimePoint = {
+  label: string;
+  scan: number;
+  rebuild: number;
+  thumbnail: number;
+  other: number;
+};
+
 export type StatsResponse = {
   overview: StatsOverview;
   reading_status: ReadingStatusStats;
@@ -581,6 +589,7 @@ export type StatsResponse = {
   by_library: LibraryStatsItem[];
   top_series: TopSeriesItem[];
   additions_over_time: MonthlyAdditions[];
+  jobs_over_time: JobTimePoint[];
   metadata: MetadataStats;
 };