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/tsconfig.json

@@ -0,0 +1,14 @@
+{
+	"extends": "./.svelte-kit/tsconfig.json",
+	"compilerOptions": {
+		"allowJs": true,
+		"checkJs": true,
+		"esModuleInterop": true,
+		"forceConsistentCasingInFileNames": true,
+		"resolveJsonModule": true,
+		"skipLibCheck": true,
+		"sourceMap": true,
+		"strict": true,
+		"moduleResolution": "bundler"
+	}
+}