refactor(i18n): update to @solid-primitives/i18n v2

[xrgzs]

由于从 @solid-primitives/i18n v1 升级到 @solid-primitives/i18n v2 涉及到 BREAKING CHANGE，i18n 实现彻底发生变化，因此特别手动处理

• 平滑更新至 vite v6
• 修复更新至 vite v6 后 es-build 检测到 useDownload.ts 中代码错误的问题
• 平滑更新至 typescript v5
• 更新 @solid-primitives/i18n v2
• 适配 @solid-primitives/i18n v2 的 i18n 写法

更新后表现与更新前几乎一致

更新了 vite v6 后开发环境下默认返回 index.html，开发预览组件时更加顺心

由于 vite-plugin-solid 这个插件说它支持 vite 3/4/5/6 ，因此暂不升级 vite 7

[Copilot]

Pull Request Overview

This PR upgrades the project’s internationalization from @solid-primitives/i18n v1 to v2 and updates related tooling (Vite v6, TypeScript v5).

• Refactored JSON language entry loading and replaced the old useI18n context with resource-based loading via createResource.
• Updated useT and SwitchLanguage hooks to use the new v2 translator API and simplified language switching.
• Fixed nullish concatenation bugs in useDownload.ts and bumped Vite, TypeScript, and plugin versions.

Reviewed Changes

Copilot reviewed 8 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/lang/en/entry.ts	Swapped dynamic glob import for explicit JSON imports; exported dict.
src/hooks/useT.ts	Rewrote translation hook using i18n.translator, resolveTemplate, and custom fallback.
src/hooks/useDownload.ts	Corrected token string building by adding parentheses around nullish coalescing.
src/components/SwitchLanguage.tsx	Removed old useI18n logic; replaced with setCurrentLang and localStorage.
src/app/index.tsx	Removed legacy I18nContext.Provider wrapper around <App />.
src/app/i18n.ts	Completely overhauled i18n context to use createResource for loading and flattening dictionaries.
src/app/App.tsx	Cleaned up old i18n imports and initialization in App.
package.json	Bumped dependencies: Vite → v6, TypeScript → v5, @solid-primitives/i18n → v2.

Files not reviewed (1)

• pnpm-lock.yaml: Language not supported

Comments suppressed due to low confidence (1)

src/components/SwitchLanguage.tsx:18

• The fetchingLang signal and its setter are declared but no longer used after refactoring. Consider removing them to avoid unused variables.

const [fetchingLang, setFetchingLang] = createSignal(false)