feat: extend the record-row design system to Host Overview, Alerts, and About

Extract the settings redesign's tokens and components into shared
static/hbd-ui.css + hbd-ui.js and dedupe settings.html against them.
About becomes yaml-key sections with kv rows; Alerts gets stat tiles,
chip filters, and alert record rows (same fetch/ack logic); Host
Overview keeps its DOM and live-update JS but is re-skinned to the
token system with a page toolbar. Live Dashboard intentionally
untouched pending its own redesign.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NfPpSpccTWBfZg1FTveyaU

hbd/server/static/hbd-ui.js

@@ -0,0 +1,16 @@
+/* hbd-ui.js — shared helpers for pages using hbd-ui.css.
+ *
+ * Keeps sticky toolbars stuck just below the fixed site nav, whose height
+ * varies with viewport width and wrapping.
+ */
+
+function _setStickyOffsets() {
+  const nav = document.querySelector('.nav');
+  const tb = document.querySelector('.st-toolbar');
+  const navH = nav ? nav.offsetHeight : 48;
+  const barsH = navH + (tb ? tb.offsetHeight : 46);
+  document.documentElement.style.setProperty('--nav-h', navH + 'px');
+  document.documentElement.style.setProperty('--bars-h', barsH + 'px');
+}
+window.addEventListener('resize', _setStickyOffsets);
+document.addEventListener('DOMContentLoaded', _setStickyOffsets);