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/schemas/user/update_profile_request.ts

@@ -0,0 +1,15 @@
+/**
+ * 更新个人资料请求
+ * 原始 Dart: UpdateProfileRequest (lib/data/models/user/user.dart)
+ */
+import { z } from "zod";
+
+export const UpdateProfileRequestSchema = z.object({
+  username: z.string().default(""),
+  nickname: z.string().default(""),
+  preferredLanguage: z.string().default(""),
+  currentMood: z.string().default(""),
+});
+
+export type UpdateProfileRequestInput = z.input<typeof UpdateProfileRequestSchema>;
+export type UpdateProfileRequestData = z.output<typeof UpdateProfileRequestSchema>;