feat(#413): add AuthProviderConfig and AuthConfigResponse types to @mosaic/shared

Refs #413

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/shared/src/types/auth.types.ts

@@ -94,3 +94,20 @@ export interface OAuthCallbackParams {
   error?: string;
   error_description?: string;
 }
+
+/**
+ * Auth provider type advertised by the backend via GET /auth/config
+ */
+export interface AuthProviderConfig {
+  id: string;
+  name: string;
+  type: "oauth" | "credentials";
+}
+
+/**
+ * Response shape for GET /auth/config
+ * Backend advertises available auth methods for the frontend to render dynamically.
+ */
+export interface AuthConfigResponse {
+  providers: AuthProviderConfig[];
+}