feat(contacts): add contacts module with backend APIs and web tab

- add user_contacts table and migration

- expose /users/contacts list/add/remove endpoints

- add Contacts tab in chat list with add/remove actions

app/users/service.py

@@ -73,3 +73,17 @@ async def has_block_relation_between_users(db: AsyncSession, *, user_a_id: int,
 
 async def list_blocked_users(db: AsyncSession, *, user_id: int) -> list[User]:
     return await repository.list_blocked_users(db, user_id=user_id)
+
+
+async def add_contact(db: AsyncSession, *, user_id: int, contact_user_id: int) -> None:
+    await repository.add_contact(db, user_id=user_id, contact_user_id=contact_user_id)
+    await db.commit()
+
+
+async def remove_contact(db: AsyncSession, *, user_id: int, contact_user_id: int) -> None:
+    await repository.remove_contact(db, user_id=user_id, contact_user_id=contact_user_id)
+    await db.commit()
+
+
+async def list_contacts(db: AsyncSession, *, user_id: int) -> list[User]:
+    return await repository.list_contacts(db, user_id=user_id)