fix: admin默认显示名改为刘通

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

backend/app/db.py

@@ -62,7 +62,7 @@ def init_db():
     if not existing:
         cursor.execute(
             'INSERT INTO users (username, display_name, password_hash, role) VALUES (?, ?, ?, ?)',
-            ('simonkoson', '蓝皓', generate_password_hash('liutong65'), 'admin')
+            ('simonkoson', '刘通', generate_password_hash('liutong65'), 'admin')
         )
 
     conn.commit()