Make the dashboard usable on phones and tablets

- Add the missing viewport meta tag; phones were rendering the desktop
  layout at 980px and shrinking it
- Add web/mobile.css (all rules inside max-width media queries, so desktop
  is unchanged):
  - data tables keep readable column widths and scroll sideways in their card
  - group headers wrap their copy buttons and stay put while tables scroll
  - Tracked Devices cards and the Documentation sidebar stack vertically
  - modals fit the screen below the fixed nav; Advanced View's three
    columns stack and the dialog scrolls as one
  - 16px inputs on phones so iOS doesn't zoom on focus
- Terminal bar: compact tabs and a dot-only LIVE indicator on narrow
  screens, taller panel in phone landscape, tighter demo dialog

web/demo/demo.css

@@ -104,6 +104,19 @@ body.usmt-term-open { padding-bottom: calc(var(--usmt-term-h, 340px) + 72px); }
 
 @media (max-width: 700px) {
     .usmt-term-legend, .usmt-term-follow { display: none; }
-    .usmt-term-tab { padding: 4px 6px; font-size: 0.75em; }
+    .usmt-term-bar { gap: 4px; padding: 0 6px; }
+    .usmt-term-toggle { padding: 4px 6px; }
+    .usmt-term-tabs { flex: 1 1 auto; overflow: hidden; }
+    .usmt-term-tab { padding: 4px 6px; font-size: 0.72em; }
+    .usmt-term-live { font-size: 0; gap: 0; }               /* just the pulsing dot */
     .usmt-term { --usmt-term-h: 45vh; }
+    .usmt-term-body { font-size: 11.5px; padding: 6px 8px 10px 14px; }
+    .usmt-term-titlebar { font-size: 0.7em; }
+    .usmt-demo-card { padding: 18px 16px; }
+    .usmt-demo-card h2 { font-size: 1.25em; }
+    .usmt-demo-actions button { flex: 1 1 auto; }
+    .usmt-demo-actions .usmt-demo-reset { margin-right: 0; }
+}
+@media (max-height: 500px) {
+    .usmt-term { --usmt-term-h: 55vh; }                   /* phones in landscape */
 }