refactor(data): split models into separate dto and schema modules

Reorganize the data layer by separating DTOs (Data Transfer Objects) from
Zod validation schemas into distinct directory structures. Previously,
all model types were imported from a single `@/data/models` barrel
file, mixing request/response classes with validation schemas.

Changes:
- Update API files (auth, chat, metrics, user) to import DTOs from
  specific paths under `@/data/dto/*` instead of the models barrel
- Move user schema to `@/data/schemas/user/user` for type-only imports
- Create dedicated Zod schema files under `@/data/schemas/*` for
  auth and chat domain models (e.g., AppleLoginRequestSchema,
  SendMessageRequestSchema, SyncMessageSchema, SttDataSchema)
- Improve discoverability and tree-shaking by co-locating schemas
  with their respective domain areas

This is a non-functional refactor that lays the groundwork for
clearer separation between transport-layer types and runtime
validation.

src/data/dto/user/user.ts

@@ -0,0 +1,59 @@
+/**
+ * 用户 DTO
+ */
+import {
+  UserSchema,
+  type UserInput,
+  type UserData,
+} from "@/data/schemas/user/user";
+import { PersonalityTraits } from "./personality_traits";
+
+export class User {
+  declare readonly id: string;
+  declare readonly username: string;
+  declare readonly email: string;
+  declare readonly platform: string;
+  declare readonly intimacy: number;
+  declare readonly dolBalance: number;
+  declare readonly relationshipStage: string;
+  declare readonly currentMood: string;
+  declare readonly personalityTraits: PersonalityTraits;
+  declare readonly preferredLanguage: string;
+  declare readonly createdAt: string;
+  declare readonly lastMessageAt: string;
+  declare readonly avatarUrl: string;
+  declare readonly loginProvider: string;
+  declare readonly isGuest: boolean;
+
+  private constructor(input: UserInput) {
+    const data = UserSchema.parse(input);
+    Object.assign(this, {
+      ...data,
+      personalityTraits: PersonalityTraits.from(data.personalityTraits),
+    });
+    Object.freeze(this);
+  }
+
+  static from(input: UserInput): User {
+    return new User(input);
+  }
+
+  static fromJson(json: unknown): User {
+    return User.from(json as UserInput);
+  }
+
+  /**
+   * 创建一个具有空 id/username 的 User 实例（用于可选 user 字段的默认占位）
+   */
+  static empty(): User {
+    return new User({ id: "", username: "" });
+  }
+
+  toJson(): UserData {
+    const { personalityTraits, ...rest } = this;
+    return {
+      ...rest,
+      personalityTraits: personalityTraits.toJson(),
+    };
+  }
+}