feat(devices): pure icon resolver + relativeTime helpers

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

public/views/icon_util.js

@@ -0,0 +1,24 @@
+// public/views/icon_util.js — pure helpers (no DOM), unit-tested.
+const GROUP_DEFAULT = {
+  Network: 'router', Entertainment: 'tv', 'Smart Home': 'plug', Personal: 'phone'
+};
+export function autoDefaultIcon(grp) {
+  return `set:devices:${GROUP_DEFAULT[grp] || 'unknown'}`;
+}
+// Note: bundled 'devices' icons are .svg; brand icons are served .png by the proxy.
+export function resolveIcon(ref) {
+  if (typeof ref !== 'string') return null;
+  let m = ref.match(/^set:([a-z0-9-]+):([a-z0-9-]+)$/);
+  if (m) return `/api/icon-sets/${m[1]}/${m[2]}.svg`;
+  m = ref.match(/^brand:([a-z0-9-]+)$/);
+  if (m) return `/api/icons/${m[1]}.png`;
+  return null;
+}
+export function relativeTime(iso, now = Date.now()) {
+  const t = typeof iso === 'number' ? iso : Date.parse(iso);
+  const s = Math.max(0, Math.floor((now - t) / 1000));
+  if (s < 60) return 'just now';
+  if (s < 3600) return `${Math.floor(s / 60)}m ago`;
+  if (s < 86400) return `${Math.floor(s / 3600)}h ago`;
+  return `${Math.floor(s / 86400)}d ago`;
+}