feat(api): expose email field in UserResponse

Cherry-picked from PR #2821 (without version bump artifacts)

app/webapi/routes/users.py

@@ -90,6 +90,7 @@ def _serialize_user(user: User) -> UserResponse:
     return UserResponse(
         id=user.id,
         telegram_id=user.telegram_id,
+        email=user.email,
         username=user.username,
         first_name=user.first_name,
         last_name=user.last_name,

app/webapi/schemas/users.py

@@ -36,6 +36,7 @@ class SubscriptionSummary(BaseModel):
 class UserResponse(BaseModel):
     id: int
     telegram_id: int | None = None
+    email: str | None = None
     username: str | None = None
     first_name: str | None = None
     last_name: str | None = None