fix: use APP_GUARD provider for global authentication guard

- Replace manual guard instantiation with DI-managed APP_GUARD provider
- Fixes request timeout issue caused by improper Passport JWT strategy initialization
- Add @Public() decorator to remaining sync endpoints for public access
- Remove unused Reflector import from main.ts

backend/src/modules/strapi.controller.ts

@@ -134,12 +134,14 @@ export class StrapiController {
   }
 
   @Post('sync/live-blogs')
+  @Public()
   async syncAllLiveBlogs() {
     await this.strapiService.syncLiveBlogs();
     return { message: 'Live blogs sync completed' };
   }
 
   @Post('sync/everything')
+  @Public()
   async syncEverything() {
     await Promise.all([
       this.strapiService.syncArticles(),