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/schemas/user/credits_history_data.ts

@@ -1,15 +0,0 @@
-/**
- * 积分历史记录模型
- * 原始 Dart: CreditsHistoryData (lib/data/models/user/user.dart)
- */
-import { z } from "zod";
-
-export const CreditsHistoryDataSchema = z.object({
-  records: z.array(z.record(z.string(), z.unknown())),
-  total: z.number(),
-  limit: z.number(),
-  offset: z.number(),
-});
-
-export type CreditsHistoryDataInput = z.input<typeof CreditsHistoryDataSchema>;
-export type CreditsHistoryDataData = z.output<typeof CreditsHistoryDataSchema>;