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/App.vue

@@ -1,7 +1,7 @@
 <script setup lang="ts">
-import zhCN from "ant-design-vue/es/locale/zh_CN";
+import zhCN from 'ant-design-vue/es/locale/zh_CN'
 
-import ImageUploadProgressOverlay from "@/components/ImageUploadProgressOverlay.vue";
+import ImageUploadProgressOverlay from '@/components/ImageUploadProgressOverlay.vue'
 </script>
 
 <template>