feat(user): implement OTP login, user creation, and profile management

- Added SendOTP method for simulating OTP sending.
- Implemented LoginWithOTP method for user login/registration via OTP, including user creation if not found.
- Added Me method to retrieve current user information.
- Implemented Update method for updating user profile details.
- Added RealName method for real-name verification.
- Implemented GetNotifications method to fetch user notifications.
- Created user_test.go for comprehensive unit tests covering login, profile retrieval, updates, real-name verification, and notifications.
- Updated database models to use appropriate consts for fields like gender, status, and roles.

backend/database/.transform.yaml

@@ -11,4 +11,22 @@ imports:
   - quyun/v2/pkg/consts
   - quyun/v2/database/fields
 field_type:
-field_relate:
+  users:
+    gender: consts.Gender
+    roles: types.Array[consts.Role]
+  contents:
+    status: consts.ContentStatus
+    visibility: consts.ContentVisibility
+    genre: string # genre is varchar(64) but no enum defined yet?
+  content_prices:
+    currency: consts.Currency
+    discount_type: consts.DiscountType
+  orders:
+    status: consts.OrderStatus
+    type: consts.OrderType
+  tenants:
+    status: consts.TenantStatus
+  tenant_users:
+    role: types.Array[consts.TenantUserRole]
+    # status: consts.UserStatus # Skipping status for now to avoid mismatch 'active' vs 'verified' without enum update
+field_relate: