feat: scaffold PulseNode dashboard (M1)

Next.js 16 + TypeScript + Tailwind v4 app with a YAML-driven config
system: schema validation (zod), .env interpolation, and a widget
registry rendering bookmark/search/group widgets. CSS custom
properties (--pn-*) drive theming and are overridable from
config.yml's theme.variables. Config load errors surface as a
readable error page instead of crashing the app.

Hot reload, docker/system/http collectors, and the WebSocket push
layer land in later milestones per the approved plan.

components/widgets/bookmark/Widget.tsx

@@ -0,0 +1,19 @@
+import type { Widget } from "@/lib/config/schema";
+
+type BookmarkWidget = Extract<Widget, { type: "bookmark" }>;
+
+export function BookmarkWidget({ widget }: { widget: BookmarkWidget }) {
+  return (
+    <a
+      href={widget.href}
+      target="_blank"
+      rel="noreferrer"
+      className="flex flex-col gap-1 rounded-[var(--radius-widget)] border border-border bg-surface p-4 transition-colors hover:border-accent"
+    >
+      <span className="text-sm font-medium text-fg">{widget.name}</span>
+      {widget.description && (
+        <span className="text-xs text-fg-muted">{widget.description}</span>
+      )}
+    </a>
+  );
+}