feat(styles): migrate design system tokens to CSS variables

Replace minimal background/foreground vars with a comprehensive design
system covering colors (background, text, brand, profile, gifts,
activities, nav), spacing, and border-radius tokens. Mirrors the
original Dart design constants under src/design/*.ts and supports
dark mode.

src/data/api/index.ts

@@ -2,4 +2,14 @@
  * @file Automatically generated by barrelsby.
  */
 
-export * from "./index";
+export * from "./api_path";
+export * from "./api_result";
+export * from "./auth_api";
+export * from "./chat_api";
+export * from "./http_client";
+export * from "./metrics_api";
+export * from "./user_api";
+export * from "./config/api_config";
+export * from "./interceptor/auth_refresh_interceptor";
+export * from "./interceptor/logging_interceptor";
+export * from "./interceptor/token_interceptor";

src/data/storage/index.ts

@@ -2,6 +2,7 @@
  * @file Automatically generated by barrelsby.
  */
 
+export * from "./auth_storage";
 export * from "./local_storage";
 export * from "./result";
 export * from "./storage_keys";