Add displayName to auth response and configurable display name claim for OIDC

- Add displayName field to AuthTokenResponse so the UI shows human-readable
  names instead of internal JWT subjects (e.g. user:oidc:<hash>)
- Add displayNameClaim to OIDC config (default: "name") allowing admins to
  configure which ID token claim contains the user's display name
- Support dot-separated claim paths (e.g. profile.display_name) like rolesClaim
- Add admin UI field for Display Name Claim on the OIDC config page
- ClickHouse migration: ALTER TABLE adds display_name_claim column

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

cameleer3-server-app/src/main/java/com/cameleer3/server/app/controller/OidcConfigAdminController.java

@@ -88,7 +88,8 @@ public class OidcConfigAdminController {
                 clientSecret,
                 request.rolesClaim() != null ? request.rolesClaim() : "realm_access.roles",
                 request.defaultRoles() != null ? request.defaultRoles() : List.of("VIEWER"),
-                request.autoSignup()
+                request.autoSignup(),
+                request.displayNameClaim() != null ? request.displayNameClaim() : "name"
         );
 
         configRepository.save(config);