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/index.html

@@ -2,6 +2,7 @@
 <html lang="en">
 <head>
     <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1">
     <title>USMT Dash</title>
     <link rel="icon" href="/favicon.png" type="image/png">
 
@@ -350,6 +351,7 @@
             .status-btn:hover { color: white; background: rgba(255,255,255,0.1); }
         }
     </style>
+    <link rel="stylesheet" href="/mobile.css">
 </head>
 <body>