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/dto/user/update_profile_request.ts

@@ -1,33 +0,0 @@
-/**
- * 更新个人资料请求 DTO
- */
-import {
-  UpdateProfileRequestSchema,
-  type UpdateProfileRequestInput,
-  type UpdateProfileRequestData,
-} from "@/data/schemas/user/update_profile_request";
-
-export class UpdateProfileRequest {
-  declare readonly username: string;
-  declare readonly nickname: string;
-  declare readonly preferredLanguage: string;
-  declare readonly currentMood: string;
-
-  private constructor(input: UpdateProfileRequestInput) {
-    const data = UpdateProfileRequestSchema.parse(input);
-    Object.assign(this, data);
-    Object.freeze(this);
-  }
-
-  static from(input: UpdateProfileRequestInput): UpdateProfileRequest {
-    return new UpdateProfileRequest(input);
-  }
-
-  static fromJson(json: unknown): UpdateProfileRequest {
-    return UpdateProfileRequest.from(json as UpdateProfileRequestInput);
-  }
-
-  toJson(): UpdateProfileRequestData {
-    return UpdateProfileRequestSchema.parse(this);
-  }
-}