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/components/MarkdownPreview.vue

@@ -1,22 +1,22 @@
 <script setup lang="ts">
-import DOMPurify from "dompurify";
-import MarkdownIt from "markdown-it";
-import { computed } from "vue";
+import DOMPurify from 'dompurify'
+import MarkdownIt from 'markdown-it'
+import { computed } from 'vue'
 
 const props = defineProps<{
-  content: string;
-}>();
+  content: string
+}>()
 
 const renderer = new MarkdownIt({
   html: true,
   linkify: true,
   breaks: true,
-});
+})
 
 const html = computed(() => {
-  const rawHtml = renderer.render(props.content || "");
-  return DOMPurify.sanitize(rawHtml);
-});
+  const rawHtml = renderer.render(props.content || '')
+  return DOMPurify.sanitize(rawHtml)
+})
 </script>
 
 <template>
@@ -92,15 +92,15 @@ const html = computed(() => {
   margin: 1.25em 0;
 }
 
-.markdown-preview :deep(p.article-editor-image[align="left"]) {
+.markdown-preview :deep(p.article-editor-image[align='left']) {
   text-align: left;
 }
 
-.markdown-preview :deep(p.article-editor-image[align="center"]) {
+.markdown-preview :deep(p.article-editor-image[align='center']) {
   text-align: center;
 }
 
-.markdown-preview :deep(p.article-editor-image[align="right"]) {
+.markdown-preview :deep(p.article-editor-image[align='right']) {
   text-align: right;
 }