refactor(data): consolidate data layer under services namespace

- Move src/data/{api,dto,schemas} directories to src/data/services/*
- Update all relative imports across the codebase to reference new paths
- Use CSS color tokens for splash button gradient in splash-button.module.css
- Add responsive sizes attribute to splash background image
- Add JSDoc documentation to splash-background component referencing original Dart implementation

src/data/services/dto/auth/refresh_token_response.ts

@@ -0,0 +1,32 @@
+/**
+ * 刷新 Token 响应 DTO
+ */
+import {
+  RefreshTokenResponseSchema,
+  type RefreshTokenResponseInput,
+  type RefreshTokenResponseData,
+} from "@/data/services/schemas/auth/refresh_token_response";
+
+export class RefreshTokenResponse {
+  declare readonly token: string;
+  declare readonly refreshToken: string;
+  declare readonly userId: string;
+
+  private constructor(input: RefreshTokenResponseInput) {
+    const data = RefreshTokenResponseSchema.parse(input);
+    Object.assign(this, data);
+    Object.freeze(this);
+  }
+
+  static from(input: RefreshTokenResponseInput): RefreshTokenResponse {
+    return new RefreshTokenResponse(input);
+  }
+
+  static fromJson(json: unknown): RefreshTokenResponse {
+    return RefreshTokenResponse.from(json as RefreshTokenResponseInput);
+  }
+
+  toJson(): RefreshTokenResponseData {
+    return RefreshTokenResponseSchema.parse(this);
+  }
+}