chore(frontend): introduce prettier + eslint and prune unused code

- Add Prettier 3 with prettier-plugin-organize-imports (sorts/removes unused imports)
- Add ESLint 10 flat config with typescript-eslint + eslint-plugin-vue + eslint-config-prettier
- Add root scripts: format, format:check, lint, lint:fix
- Reformat 257 files across admin-web, ops-web, desktop-client, packages
- Remove unused locals/exports flagged by --noUnusedLocals/--noUnusedParameters
- Fix duplicate localTabLabel key, surrogate-pair regex u-flag, NBSP literal in regex
- Skip server/ (Go) and apps/browser-extension/ (deprecated per ADR)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/admin-web/src/i18n/index.ts

@@ -1,14 +1,14 @@
-import { createI18n } from "vue-i18n";
+import { createI18n } from 'vue-i18n'
 
-import zhCN from "./messages/zh-CN";
+import zhCN from './messages/zh-CN'
 
-const APP_LOCALE = "zh-CN";
+const APP_LOCALE = 'zh-CN'
 
 export const i18n = createI18n({
   legacy: false,
   locale: APP_LOCALE,
   fallbackLocale: APP_LOCALE,
   messages: {
-    "zh-CN": zhCN,
+    'zh-CN': zhCN,
   },
-});
+})