refactor: fix bugs et réduire duplication + extraire modales BrowseComponent

- fix(dto): ajouter @IsEmail() sur contactFunctionalEmail/TechnicalEmail dans UpdateApiEntryDto
- fix(docs): corriger stringify des erreurs (String(error) → error.message)
- refactor(mapper): extraire toApiEntryListItem() dans api-entry.mapper.ts partagé
- refactor(categories): supprimer CONVENTION_LABELS et toApiEntryListItem locaux dupliqués
- refactor(browse): extraire CategoryFormModalComponent et CategoryDeleteModalComponent
- refactor(api-detail): convertir editPreviewTitle() en computed()

Generated with [Claude Code](https://claude.ai/code)
via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

back/src/modules/docs-generation/docs-generation.service.ts

@@ -46,7 +46,7 @@ export class DocsGenerationService {
     } catch (error) {
       await this.apisService.updateInternal(entryId, {
         status: 'ERROR',
-        errorMessage: String(error),
+        errorMessage: error instanceof Error ? error.message : String(error),
       });
     }
   }