feat: add User ID Claim field to OIDC admin config UI

New input in the Claim Mapping section lets admins configure which
id_token claim is used as the unique user identifier (default: sub).

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

ui/src/api/schema.d.ts

@@ -1444,6 +1444,7 @@ export interface components {
             defaultRoles?: string[];
             autoSignup?: boolean;
             displayNameClaim?: string;
+            userIdClaim?: string;
         };
         /** @description Error response */
         ErrorResponse: {
@@ -1460,6 +1461,7 @@ export interface components {
             defaultRoles?: string[];
             autoSignup?: boolean;
             displayNameClaim?: string;
+            userIdClaim?: string;
         };
         UpdateGroupRequest: {
             name?: string;