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/layout/Dashboard.tsx

@@ -0,0 +1,15 @@
+import type { Config } from "@/lib/config/schema";
+import { GroupSection } from "./GroupSection";
+
+export function Dashboard({ config }: { config: Config }) {
+  return (
+    <main className="mx-auto flex max-w-6xl flex-col gap-8 px-6 py-10">
+      <header className="flex items-center justify-between">
+        <h1 className="text-lg font-semibold text-fg">{config.settings.title}</h1>
+      </header>
+      {config.groups.map((group) => (
+        <GroupSection key={group.name} group={group} />
+      ))}
+    </main>
+  );
+}

components/layout/GroupSection.tsx

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+import type { Group } from "@/lib/config/schema";
+import { widgetRegistry } from "@/components/widgets/registry";
+
+export function GroupSection({ group }: { group: Group }) {
+  return (
+    <section className="flex flex-col gap-3">
+      <h2 className="text-xs font-semibold tracking-wide text-fg-muted uppercase">
+        {group.name}
+      </h2>
+      <div className="grid grid-cols-[repeat(auto-fill,minmax(220px,1fr))] gap-3">
+        {group.widgets.map((widget, index) => {
+          const Component = widgetRegistry[widget.type];
+          return <Component key={index} widget={widget as never} />;
+        })}
+      </div>
+    </section>
+  );
+}

components/layout/ThemeStyleInjector.tsx

@@ -0,0 +1,8 @@
+export function ThemeStyleInjector({ variables }: { variables: Record<string, string> }) {
+  const entries = Object.entries(variables);
+  if (entries.length === 0) return null;
+
+  const css = `:root{${entries.map(([key, value]) => `${key}:${value};`).join("")}}`;
+
+  return <style id="pulsenode-theme-overrides" dangerouslySetInnerHTML={{ __html: css }} />;
+}