feat(contacts): switch contacts UX to email-first flow

- expose email in user search/contact responses

- add add-contact-by-email API endpoint

- show email in contacts/search and add contact form by email in Contacts tab

app/users/repository.py

@@ -43,7 +43,12 @@ async def search_users_by_username(
     exclude_user_id: int | None = None,
 ) -> list[User]:
     normalized = query.lower().strip().lstrip("@")
-    stmt = select(User).where(func.lower(User.username).like(f"%{normalized}%"))
+    stmt = select(User).where(
+        or_(
+            func.lower(User.username).like(f"%{normalized}%"),
+            func.lower(User.email).like(f"%{normalized}%"),
+        )
+    )
     if exclude_user_id is not None:
         stmt = stmt.where(User.id != exclude_user_id)
     stmt = stmt.order_by(User.username.asc()).limit(limit)

app/users/router.py

@@ -4,11 +4,12 @@ from sqlalchemy.ext.asyncio import AsyncSession
 from app.auth.service import get_current_user
 from app.database.session import get_db
 from app.users.models import User
-from app.users.schemas import UserProfileUpdate, UserRead, UserSearchRead
+from app.users.schemas import ContactByEmailRequest, UserProfileUpdate, UserRead, UserSearchRead
 from app.users.service import (
     add_contact,
     block_user,
     get_user_by_id,
+    get_user_by_email,
     get_user_by_username,
     list_blocked_users,
     list_contacts,
@@ -101,6 +102,23 @@ async def add_contact_endpoint(
     await add_contact(db, user_id=current_user.id, contact_user_id=user_id)
 
 
+@router.post("/contacts/by-email", status_code=status.HTTP_204_NO_CONTENT)
+async def add_contact_by_email_endpoint(
+    payload: ContactByEmailRequest,
+    db: AsyncSession = Depends(get_db),
+    current_user: User = Depends(get_current_user),
+) -> None:
+    target = await get_user_by_email(db, payload.email)
+    if not target:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="User not found")
+    if target.id == current_user.id:
+        raise HTTPException(status_code=status.HTTP_422_UNPROCESSABLE_ENTITY, detail="Cannot add yourself")
+    is_blocked = await has_block_relation_between_users(db, user_a_id=current_user.id, user_b_id=target.id)
+    if is_blocked:
+        raise HTTPException(status_code=status.HTTP_409_CONFLICT, detail="Cannot add contact while blocked")
+    await add_contact(db, user_id=current_user.id, contact_user_id=target.id)
+
+
 @router.delete("/{user_id}/contacts", status_code=status.HTTP_204_NO_CONTENT)
 async def remove_contact_endpoint(
     user_id: int,

app/users/schemas.py

@@ -40,4 +40,9 @@ class UserSearchRead(BaseModel):
     id: int
     name: str
     username: str
+    email: EmailStr
     avatar_url: str | None = None
+
+
+class ContactByEmailRequest(BaseModel):
+    email: EmailStr