chore(frontend): engineering baseline per guide ch.8

- toolchain: vitest+jsdom (15 tests green: permission pure functions
  exhaustive, storage migration), prettier (printWidth 120 to fit the
  dense existing style + 700-line page budget), commitlint conventional
- npm scripts: typecheck / format / test / lint:fix; build fingerprint
  __APP_VERSION__ (version+git hash+build time) shown in Settings > about
- git hooks via core.hooksPath=frontend/.husky: pre-commit lint-staged
  (prettier + eslint --fix best-effort), commit-msg commitlint
- permission pure functions extracted to lib/permissions.ts (single
  source consumed by useAuth/useLogin); AuditLogsPage filters on URL
- backend: resp package unit tests; health version constant aligned
  with frontend package.json

frontend/.husky/pre-commit

@@ -0,0 +1,3 @@
+#!/usr/bin/env sh
+# 快修复层:staged 文件 prettier 格式化;eslint --fix 尽力修复(存量 any/空 catch 不阻塞)
+cd "$(dirname "$0")/../" && npx lint-staged