feat(web): add configurable enter behavior setting

[junxin367]

概要

我根据 #570 在 Web 设置中增加了“回车键行为”设置，默认仍为“发送消息”，也可以切换为“插入换行”。

变更内容

• 在设置页新增“聊天 / 回车键行为”配置项
• 新增 useComposerEnterBehavior，使用 localStorage 持久化用户选择
• 在 HappyComposer 中接入两种输入模式：
  • send：Enter 发送，Shift+Enter 换行
  • newline：Enter 换行，Ctrl/Cmd+Enter 发送
• 保持 IME 输入法处理和自动补全 suggestion 的 Enter 优先级不变
• 补齐中英文 i18n 文案
• 增加对应测试

验证

• cd web && bun run test
• cd web && bun run typecheck

Closes #570

[github-actions]

Findings

• No issues found with confidence >= 80% in the added/modified lines.

Summary

• Review mode: initial
• Reviewed the latest PR diff in full for the Web enter-behavior setting, including the new localStorage hook, settings UI wiring, i18n strings, and HappyComposer Enter handling. Residual risk: the added tests cover storage/options and settings rendering, but not the composer keydown behavior itself.

Testing

• Not run (automation): bun is not installed in this runner image, so bun --cwd web run test -- src/hooks/useComposerEnterBehavior.test.ts src/routes/settings/index.test.tsx and bun --cwd web run typecheck could not execute.

HAPI Bot