feat(hub): migrate database admin pages to SPA (database-admin)

- scaffold hub/database-admin as SvelteKit 2 + Svelte 5 static SPA
  with aurora/glass visual style (paths.base='/database')
- add lib/{api,session,org}.ts + Aurora.svelte component
- add routes: root redirect, /admin login page, /dashboard (OWNER/ADMIN only)
- backend: replace server-rendered HTML routes with /database/config JSON endpoint
- add hub/src/database/static.ts to serve SPA under /database/*
- wire registerDatabaseSpa into plugin.ts
- exempt /database/* from silo rate-limit (same treatment as /admin/*)
- add database:dev + database:build npm scripts; update deploy scripts
- update hub/src/database/README.md

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

hub/database-admin/svelte.config.js

@@ -0,0 +1,22 @@
+import adapter from '@sveltejs/adapter-static';
+import { vitePreprocess } from '@sveltejs/vite-plugin-svelte';
+
+/** @type {import('@sveltejs/kit').Config} */
+const config = {
+	preprocess: vitePreprocess(),
+	kit: {
+		adapter: adapter({
+			pages: 'build',
+			assets: 'build',
+			fallback: 'index.html',
+			precompress: false,
+			strict: false,
+		}),
+		// This SPA is served under /database by the Hub. admin-web owns the
+		// root asset paths (/_app, /favicon.svg); a base path moves this app's
+		// assets to /database/_app/* so the two builds never collide.
+		paths: { base: '/database' },
+	},
+};
+
+export default config;