refactor: Phase E — types de réponses API standardisés + SVGs inline → Icon

E1 - API responses:
- Crée responses.rs avec OkResponse, DeletedResponse, UpdatedResponse,
  RevokedResponse, UnlinkedResponse, StatusResponse (6 tests de sérialisation)
- Remplace ~15 json!() inline par des types structurés dans books, libraries,
  tokens, users, handlers, anilist, metadata, download_detection, torrent_import
- Signatures de retour des handlers typées (plus de serde_json::Value)

E2 - SVGs → Icon component:
- Ajoute icon "lock" au composant Icon
- Remplace ~30 SVGs inline par <Icon> dans 9 composants
  (FolderPicker, FolderBrowser, LiveSearchForm, JobRow, LibraryActions,
  ReadingStatusModal, EditBookForm, EditSeriesForm, UserSwitcher)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/backoffice/app/components/JobRow.tsx

@@ -279,9 +279,7 @@ export function JobRow({ job, libraryName, highlighted, onCancel, onReplay, form
                 size="xs"
                 onClick={() => onCancel(job.id)}
               >
-                <svg className="w-3.5 h-3.5 mr-1.5" fill="none" stroke="currentColor" viewBox="0 0 24 24">
-                  <path strokeLinecap="round" strokeLinejoin="round" strokeWidth={2} d="M6 18L18 6M6 6l12 12" />
-                </svg>
+                <Icon name="x" size="sm" className="!w-3.5 !h-3.5 mr-1.5" />
                 {t("common.cancel")}
               </Button>
             )}