feat(dashboard): scaffold SvelteKit SPA for control plane

SvelteKit 2 + Svelte 5 (runes) + TS, built with `adapter-static`
into a single SPA bundle that Caddy serves verbatim in production.
The dashboard targets only `/api/admin/*` (manager); data-plane
invocations go through the orchestrator, not through here.

  * Vite dev server proxies `/api` and `/healthz` to PICLOUD_API
    (default `http://127.0.0.1:18080` to match the picloud bind
    override). Port configurable via PICLOUD_DASHBOARD_PORT.
  * `src/lib/api.ts` is a thin typed client over the control-plane
    paths; the scripts placeholder route shows the "load → error →
    list" shape so the missing-API state is informative, not blank.
  * SSR disabled at the layout level: the build is a pure SPA, no
    Node runtime is required at serve time.
  * `npm run check` and `npm run build` both green; `npm audit`
    clean (cookie override pins past the SvelteKit transitive
    advisory that doesn't apply in SPA mode).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

dashboard/svelte.config.js

@@ -0,0 +1,21 @@
+import adapter from '@sveltejs/adapter-static';
+import { vitePreprocess } from '@sveltejs/vite-plugin-svelte';
+
+/** @type {import('@sveltejs/kit').Config} */
+const config = {
+	preprocess: vitePreprocess(),
+	kit: {
+		// SPA build: Caddy serves these files in prod, falls back to
+		// index.html for client-side routing. Matches our architecture
+		// — the dashboard is a pure SPA against /api/admin/*.
+		adapter: adapter({
+			fallback: 'index.html',
+			pages: 'build',
+			assets: 'build',
+			precompress: false,
+			strict: false
+		})
+	}
+};
+
+export default config;