feat(ui): phase 5 — graphs, widgets, theming, PWA, boards, i18n

P5a: 24h uptime bar strip + latency chart on monitor detail, iframe
embed widget, generic JSON-path widget, accent/wallpaper/custom CSS
settings, PWA manifest + service worker, demo GIF.

P5b: transport picker + per-transport fields + test button in
settings; per-monitor alert-rule fields in dialogs.

P5c: container cpu/mem columns, SMART/ZFS/GPU sections on system
detail, subdomains section on domain detail.

P5d: login/setup page + auth middleware client handling, board
switcher + /b/:slug routes, full string extraction to typed t() keys
with {param} interpolation, complete cs locale, language select.

Authored By: TDvorak <[email protected]>

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

apps/frontend/index.html

@@ -3,6 +3,10 @@
   <head>
     <meta charset="UTF-8" />
     <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <meta name="theme-color" content="#0a0a0a" />
+    <link rel="manifest" href="/manifest.webmanifest" />
+    <link rel="icon" href="/icon.svg" type="image/svg+xml" />
+    <link rel="apple-touch-icon" href="/icon-192.png" />
     <title>Dash</title>
     <script>
       // Pre-paint theme: localStorage mirrors the server setting, applied