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.
