Make About bootstrap fallback visible and recoverable

[cauyxy]

Summary

• model About bootstrap as explicit loading, authoritative, fallback, and blocking resource states
• keep packaged version data usable while labeling its source and unavailable fields
• localize semantic failures, diagnostics, and in-place retry recovery in Chinese and English
• update frontend architecture and verification truth

Testing

• npm run check
• npx vitest run src/features/about/appBootstrap.test.ts src/features/about/aboutProblems.test.ts src/pages/About.test.tsx src/layouts/ShellHeader.test.tsx
• npm run test:unit
• npm run verify -- --source-only
• Browser Preview smoke test at http://127.0.0.1:14207/about (fallback provenance, unavailable BPP version, zh/en locale switch, selectable version text, no horizontal overflow)
• macOS Tauri smoke test (authoritative native source, app 4.5.0, bundled BPP 4.5.0.prod)

Closes #30

Release Notes:

• About now identifies fallback version information and offers localized recovery when native app details cannot be loaded.