[Bug/Feature] 日语罗马字输入不支持训令式(如 つ 无法用 tu 输入)

Issue Description In the Japanese word practice mode, the Roman input currently seems to support only the Hepburn Romanization scheme, not the Japanese/JIS Romanization scheme. For example:

• つ can only be input as tsu, not tu
• Similarly, し(shi/si), ち(chi/ti), and ふ(fu/hu) may have the same problem with kana Expectation We hope to support the input determination of both the Hepburn and JIS Romanization schemes, meaning that both are considered correct, for example, つ can be input as tsu or tu. This will be more friendly for users who learn JIS Romanization, which is the official standard in Japanese compulsory education, and differs from the internationally accepted Hepburn Romanization in some kana spelling. It is recommended to add an option to switch Romanization schemes in the settings, or to directly implement input tolerance (both spellings are acceptable).