feat: phase 2 widgets — registry, fetchers, clock, config dialog

Backend: internal/widget registry (type metadata + Fetcher), Pi-hole
v5 / AdGuard / Immich fetchers, /api/widgets/types + /api/widgets/:id/data
with 30s TTL cache (failures cached too), kind+config on item create/patch.
Config secrets are never logged or echoed in errors.

Frontend: WidgetContent host maps config.type to a component, polls
/data every 30s for server-backed types; clock renders client-side.
Generic WidgetDialog builds its form from the registry's field list.
Widget tiles are sortable items in both renderers.

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

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

apps/frontend/src/widgets/immich.tsx

@@ -0,0 +1,35 @@
+import type { Item } from "@/types";
+import type { WidgetData } from "@/widgets/index";
+
+// Immich — photo/video counts and library footprint.
+
+function num(d: WidgetData | undefined, k: string): number {
+	const v = d?.[k];
+	return typeof v === "number" ? v : 0;
+}
+
+const fmtNum = (n: number) =>
+	n >= 1_000_000 ? `${(n / 1_000_000).toFixed(1)}M` : n >= 1000 ? `${(n / 1000).toFixed(1)}k` : String(n);
+
+const fmtBytes = (b: number) =>
+	b >= 1 << 30 ? `${(b / (1 << 30)).toFixed(1)} GB` : `${(b / (1 << 20)).toFixed(0)} MB`;
+
+export function ImmichWidget({ item, data, error }: { item: Item; data: WidgetData | undefined; error: string | undefined }) {
+	if (error) {
+		return <span className="font-mono text-[11px] text-text-faint">{item.name} — {error}</span>;
+	}
+	return (
+		<div className="flex min-w-0 items-center gap-4">
+			<div className="flex min-w-0 flex-col gap-0.5">
+				<span className="font-mono text-[22px] font-medium leading-none tracking-tight tabular-nums">
+					{data ? fmtNum(num(data, "photos")) : "…"}
+				</span>
+				<span className="text-[10.5px] uppercase tracking-[0.1em] text-text-faint">photos</span>
+			</div>
+			<div className="ml-auto flex flex-col items-end gap-1 font-mono text-[10.5px] text-text-faint">
+				<span>{fmtNum(num(data, "videos"))} videos</span>
+				<span>{fmtBytes(num(data, "usageBytes"))}</span>
+			</div>
+		</div>
+	);
+}