feat(auth): automatically assign admin role to the first registered user

backend/core/database.py

@@ -216,6 +216,18 @@ async def list_users(
     return list(result.scalars().all())
 
 
+async def count_users(
+    session: AsyncSession | None = None,
+) -> int:
+    """Return the total number of users (including inactive)."""
+    if session is None:
+        async with _session_factory() as session:
+            result = await session.execute(select(User))
+            return len(result.scalars().all())
+    result = await session.execute(select(User))
+    return len(result.scalars().all())
+
+
 async def update_user(
     user_id: uuid.UUID,
     session: AsyncSession,

backend/routes/auth.py

@@ -91,11 +91,17 @@ async def register_endpoint(
             detail=f"User '{body.username}' already exists",
         )
 
+    # First user to register becomes an admin automatically.
+    from backend.core.database import count_users
+
+    total_users = await count_users(session=session)
+    role = "admin" if total_users == 0 else body.role
+
     user = await create_user_with_password(
         username=body.username,
         display_name=body.display_name,
         password=body.password,
-        role=body.role,
+        role=role,
         team=body.team,
         session=session,
     )