OTP Input component

**Is your feature request related to a problem? Please describe.**
OTP / verification code input is a common requirement, but react-native-paper does not provide a dedicated component. Developers must build custom solutions or rely on third-party libraries.

**Describe the solution you'd like**
Add a built-in OTP Input component that works with the existing react-native-paper theme and components.

**Describe alternatives you've considered**
Using third-party libraries.

**Additional context**
This is a common pattern in authentication flows (login, signup, 2FA) and would improve consistency and developer experience.

该 issue 未指定任何文件、测试或入口点。首先检查现有的 react-native-paper 组件和主题集成，以确定 OTP Input 组件的范围和 API。完成这项工作需要达成一致的设计，并提供一个与现有主题和组件一致工作的内置组件。

由索引模型根据 Issue 内容生成。