Refactor: Use common password validator

Refactors password validation logic to use a common `PasswordValidator` utility. This ensures consistent password validation rules across different parts of the application, including:

- User login
- Email sign-up
- Password change
- Account removal

Also adds a string resource for password too long error message.

app/src/main/res/values/strings.xml

@@ -185,5 +185,6 @@
     <string name="group_room_enter_fail">加入房间失败</string>
     <string name="agent_createing">创建中...</string>
     <string name="agent_find">发现</string>
+    <string name="text_error_password_too_long">Password cannot exceed %1$d characters</string>
 
 </resources>