feat: implement authentication system for API Gateway and FileService

- Add JWT Bearer token validation to API Gateway with restricted CORS
- Add cookie-based JWT validation to FileService for browser image requests
- Create shared authentication infrastructure in FictionArchive.Service.Shared
- Update frontend to set fa_session cookie after OIDC login
- Add [Authorize] attributes to GraphQL mutations with role-based restrictions
- Configure OIDC settings for both services in docker-compose

Implements FA-17: Authentication for microservices architecture

FictionArchive.Service.NovelService/GraphQL/Mutation.cs

@@ -6,17 +6,20 @@ using FictionArchive.Service.NovelService.Models.SourceAdapters;
 using FictionArchive.Service.NovelService.Services;
 using FictionArchive.Service.NovelService.Services.SourceAdapters;
 using FictionArchive.Service.Shared.Services.EventBus;
+using HotChocolate.Authorization;
 using Microsoft.EntityFrameworkCore;
 
 namespace FictionArchive.Service.NovelService.GraphQL;
 
 public class Mutation
 {
+    [Authorize(Roles = "admin")]
     public async Task<NovelUpdateRequestedEvent> ImportNovel(string novelUrl, NovelUpdateService service)
     {
         return await service.QueueNovelImport(novelUrl);
     }
 
+    [Authorize]
     public async Task<ChapterPullRequestedEvent> FetchChapterContents(uint novelId,
         uint chapterNumber,
         NovelUpdateService service)