feat(ui): design polish — semantic status tokens, self-hosted fonts, a11y, skeletons

Design system & theme:
- add semantic status tokens (success/warning/danger + track) for both themes
- replace hardcoded green/red/amber/blue across ~20 files with tokens
- fix light-mode bugs (bg-white/10, rgba white gauges) via theme-aware track
- add named text-2xs (11px) step; unify ad-hoc text-[10px]/[11px]
- consistent card elevation (shadow-sm) + opt-in interactive hover

Fonts & perf:
- self-host DM Sans / JetBrains Mono via @fontsource-variable (font-display: swap)
- drop render-blocking Google Fonts link; remove unused Geist dep

Accessibility & mobile:
- global prefers-reduced-motion; focus-visible on custom buttons
- StatusDot role/aria-label; aria-sort on sortable table headers
- Button auto nativeButton=false when rendered as Link/anchor
- 100vh -> dvh in app shell; pointer-coarse min 44px touch targets

Loading & types:
- Skeleton primitive + table loading state on InstancesPage
- fix all 36 pre-existing tsc errors (Select null coercion, SDN query keys,
  Dashboard Rec typing, VMInstance, profile language, JSX namespace)

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

frontend/index.html

@@ -4,9 +4,7 @@
     <meta charset="UTF-8" />
     <link rel="icon" type="image/x-icon" href="/favicon.ico" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
-    <link rel="preconnect" href="https://fonts.googleapis.com" />
-    <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin />
-    <link href="https://fonts.googleapis.com/css2?family=DM+Sans:ital,opsz,wght@0,9..40,100..1000;1,9..40,100..1000&family=JetBrains+Mono:wght@400;500&display=swap" rel="stylesheet" />
+    <!-- Fonts are self-hosted via @fontsource-variable (imported in main.tsx) -->
     <title>PVEmanager</title>
   </head>
   <body>