fix: use badge for stack on detail overview, consistent across all views

stack was plain highlighted text on the detail page but a coloured badge
on the home cards and in the history timeline. Now all three use the same
badge component.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

js/ui.js

@@ -178,7 +178,7 @@ async function renderDetailPage(vmid) {
   document.getElementById('detail-identity').innerHTML = `
     <div class="kv-row"><span class="kv-key">name</span><span class="kv-val highlight">${esc(inst.name)}</span></div>
     <div class="kv-row"><span class="kv-key">state</span><span class="kv-val"><span class="badge ${esc(inst.state)}">${esc(inst.state)}</span></span></div>
-    <div class="kv-row"><span class="kv-key">stack</span><span class="kv-val highlight">${esc(inst.stack) || '—'}</span></div>
+    <div class="kv-row"><span class="kv-key">stack</span><span class="kv-val"><span class="badge ${esc(inst.stack)}">${esc(inst.stack) || '—'}</span></span></div>
     <div class="kv-row"><span class="kv-key">vmid</span><span class="kv-val highlight">${inst.vmid}</span></div>
     <div class="kv-row"><span class="kv-key">internal id</span><span class="kv-val">${inst.id}</span></div>
   `;