feat: redesign jobs page action bar with grouped layout

Replace flat button row + separate reference card with a single card
organized in 3 visual groups (Indexation, Thumbnails, Metadata).
Each action is a card-like button with inline description.
Destructive actions have distinct warning styling.

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

apps/backoffice/lib/i18n/en.ts

@@ -176,6 +176,16 @@ const en: Record<TranslationKey, string> = {
   "jobs.refreshMetadata": "Refresh metadata",
   "jobs.refreshMetadataDescription": "Refreshes metadata for all series already linked to an external provider. Re-downloads information from the provider and updates series and books in the database (respecting locked fields). Series without an approved link are ignored. <strong>Requires a specific library</strong> (does not work on \"All libraries\").",
   "jobs.referenceTitle": "Job types reference",
+  "jobs.groupIndexation": "Indexation",
+  "jobs.groupThumbnails": "Thumbnails",
+  "jobs.groupMetadata": "Metadata",
+  "jobs.requiresLibrary": "Requires a specific library",
+  "jobs.rebuildShort": "Scan new & modified files",
+  "jobs.fullRebuildShort": "Delete all & re-scan from scratch",
+  "jobs.generateThumbnailsShort": "Missing thumbnails only",
+  "jobs.regenerateThumbnailsShort": "Recreate all thumbnails",
+  "jobs.batchMetadataShort": "Auto-match unlinked series",
+  "jobs.refreshMetadataShort": "Update existing linked series",
   "jobs.rebuildDescription": "Incremental scan: detects files added, modified, or deleted since the last scan, indexes them, and generates missing thumbnails. Existing unmodified data is preserved. This is the most common and fastest action.",
   "jobs.fullRebuildDescription": "Deletes all indexed data (books, series, thumbnails) then performs a full scan from scratch. Useful if the database is out of sync or corrupted. Long and destructive operation: reading statuses and manual metadata will be lost.",
   "jobs.generateThumbnailsDescription": "Generates thumbnails only for books that don't have one yet. Existing thumbnails are not affected. Useful after an import or if some thumbnails are missing.",