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/public/icon.svg

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