feat: add batch metadata jobs, series filters, and translate backoffice to French

- Add metadata_batch job type with background processing via tokio::spawn
- Auto-apply metadata only when single result at 100% confidence
- Support primary + fallback provider per library, "none" to opt out
- Add batch report/results API endpoints and job detail UI
- Add series_status and has_missing filters to both series listing pages
- Add GET /series/statuses endpoint for dynamic filter options
- Normalize series_metadata status values (migration 0036)
- Hide ComicVine provider tab when no API key configured
- Translate entire backoffice UI from English to French

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

apps/backoffice/app/components/LiveSearchForm.tsx

@@ -120,7 +120,7 @@ export function LiveSearchForm({ fields, basePath, debounceMs = 300 }: LiveSearc
             w-full sm:w-auto
           "
         >
-          Clear
+          Effacer
         </button>
       )}
     </form>