add admin user management: list and delete registered users

sentence_api/repository.py

@@ -805,6 +805,25 @@ class VideoRepository:
             ).fetchone()
         return dict(row) if row else None
 
+    def list_users(self) -> List[Dict[str, Any]]:
+        with self._connect() as connection:
+            rows = connection.execute(
+                """
+                SELECT u.id, u.username, u.nickname, u.phone, u.created_at,
+                       COUNT(DISTINCT e.video_hash) AS enrollment_count
+                FROM users u
+                LEFT JOIN enrollments e ON e.user_id = u.id
+                GROUP BY u.id
+                ORDER BY u.created_at DESC
+                """
+            ).fetchall()
+        return [dict(row) for row in rows]
+
+    def delete_user(self, user_id: str) -> bool:
+        with self._connect() as connection:
+            cursor = connection.execute("DELETE FROM users WHERE id = ?", (user_id,))
+        return cursor.rowcount > 0
+
     def authenticate_user(self, username: str, password: str) -> Optional[Dict[str, Any]]:
         with self._connect() as connection:
             row = connection.execute(