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/src/routes/+page.svelte

@@ -0,0 +1,30 @@
+<script lang="ts">
+	import { onMount } from 'svelte';
+	import { goto } from '$app/navigation';
+	import { base } from '$app/paths';
+	import { api } from '$lib/api';
+
+	onMount(async () => {
+		// /database entry — route to dashboard if signed in, else the login page.
+		try {
+			await api.me();
+			await goto(`${base}/dashboard`, { replaceState: true });
+		} catch {
+			await goto(`${base}/admin`, { replaceState: true });
+		}
+	});
+</script>
+
+<div class="flex min-h-screen items-center justify-center">
+	<div class="flex flex-col items-center gap-3 text-slate-400">
+		<svg class="h-7 w-7 animate-spin text-violet-500" viewBox="0 0 24 24" fill="none">
+			<circle class="opacity-25" cx="12" cy="12" r="10" stroke="currentColor" stroke-width="4"></circle>
+			<path
+				class="opacity-90"
+				fill="currentColor"
+				d="M4 12a8 8 0 018-8V0C5.373 0 0 5.373 0 12h4zm2 5.291A7.962 7.962 0 014 12H0c0 3.042 1.135 5.824 3 7.938l3-2.647z"
+			></path>
+		</svg>
+		<p class="text-sm">正在进入…</p>
+	</div>
+</div>