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.FileService/appsettings.json

@@ -18,5 +18,14 @@
     "AccessKey": "REPLACE_ME",
     "SecretKey": "REPLACE_ME"
   },
+  "OIDC": {
+    "Authority": "https://auth.orfl.xyz/application/o/fictionarchive/",
+    "ClientId": "fictionarchive-files",
+    "Audience": "fictionarchive-api",
+    "ValidateIssuer": true,
+    "ValidateAudience": true,
+    "ValidateLifetime": true,
+    "ValidateIssuerSigningKey": true
+  },
   "AllowedHosts": "*"
 }