refactor(admin-web): move answer markdown normalization to a tested lib

Extract normalizeLooseMarkdownLine from TrackingQuestionDetailView into
a shared monitoring-answer-markdown module and harden it (model bullet
`**-` and `*` handling). Add a vitest runner and unit tests for the
normalization rules.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/admin-web/package.json

@@ -5,6 +5,7 @@
   "type": "module",
   "scripts": {
     "dev": "vite",
+    "test": "vitest run",
     "build": "vue-tsc --noEmit && vite build",
     "build:analyze": "vue-tsc --noEmit && ANALYZE=true vite build",
     "preview": "vite preview",
@@ -43,6 +44,7 @@
     "typescript": "^5.9.3",
     "vite": "^7.3.2",
     "vite-plugin-compression2": "^2.5.3",
+    "vitest": "^4.1.5",
     "vue-tsc": "^3.2.6"
   }
 }