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/src/widgets/jsonpath.tsx

@@ -0,0 +1,22 @@
+import type { WidgetData } from "@/widgets";
+import type { Item } from "@/types";
+
+// JSON value — renders the scalar the backend extracted at config.path.
+export function JsonPathWidget({ item, data, error }: {
+	item: Item;
+	data: WidgetData | undefined;
+	error: string | undefined;
+}) {
+	const label = typeof data?.label === "string" && data.label ? data.label : item.name;
+	const value = data?.value;
+	return (
+		<div className="flex min-w-0 flex-col justify-center gap-0.5">
+			<span className="truncate text-[10.5px] uppercase tracking-[0.1em] text-text-faint">
+				{label}
+			</span>
+			<span className="truncate font-mono text-[18px] font-medium leading-tight">
+				{error ? "err" : value === undefined ? "…" : typeof value === "object" ? JSON.stringify(value) : String(value)}
+			</span>
+		</div>
+	);
+}