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/sw.js

@@ -0,0 +1,57 @@
+// Dash service worker: cache-first for static assets, network-first for /api.
+// Bump CACHE on each deploy shape change; clients drop stale caches on activate.
+const CACHE = "dash-v1";
+const ASSET = /\.(?:js|css|woff2?|png|svg|webmanifest|ico)$/;
+
+self.addEventListener("install", (e) => {
+	self.skipWaiting();
+	e.waitUntil(caches.open(CACHE).then((c) => c.add("/")));
+});
+
+self.addEventListener("activate", (e) => {
+	e.waitUntil(
+		caches.keys()
+			.then((keys) => Promise.all(keys.filter((k) => k !== CACHE).map((k) => caches.delete(k))))
+			.then(() => self.clients.claim()),
+	);
+});
+
+self.addEventListener("fetch", (e) => {
+	const url = new URL(e.request.url);
+	if (e.request.method !== "GET" || url.origin !== self.location.origin) return;
+
+	// API: network-first so widgets stay live; fall back to cache offline.
+	if (url.pathname.startsWith("/api/")) {
+		e.respondWith(
+			fetch(e.request)
+				.then((res) => {
+					const clone = res.clone();
+					if (res.ok) caches.open(CACHE).then((c) => c.put(e.request, clone));
+					return res;
+				})
+				.catch(() => caches.match(e.request)),
+		);
+		return;
+	}
+
+	// Navigations: network-first, fall back to cached "/" (read-only offline).
+	if (e.request.mode === "navigate") {
+		e.respondWith(fetch(e.request).catch(() => caches.match("/")));
+		return;
+	}
+
+	// Static assets: cache-first, populate on miss.
+	if (ASSET.test(url.pathname)) {
+		e.respondWith(
+			caches.match(e.request).then(
+				(hit) =>
+					hit ||
+					fetch(e.request).then((res) => {
+						const clone = res.clone();
+						if (res.ok) caches.open(CACHE).then((c) => c.put(e.request, clone));
+						return res;
+					}),
+			),
+		);
+	}
+});