fix(api): return real total for user pagination

app/infra/db/metadb/repositories/metadata_repository.py

@@ -4,7 +4,7 @@ from typing import Optional, List
 from uuid import UUID, uuid4
 
 from cryptography.fernet import InvalidToken
-from sqlalchemy import delete, select
+from sqlalchemy import delete, func, select
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.core.encryption import (
@@ -122,6 +122,12 @@ class MetadataRepository:
         )
         return list(result.scalars().all())
 
+    async def count_users(self) -> int:
+        result = await self.session.execute(
+            select(func.count()).select_from(models.User)
+        )
+        return int(result.scalar() or 0)
+
     async def upsert_user_from_keycloak(
         self,
         *,