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/package.json

@@ -33,7 +33,7 @@
   "description": "Curriculum Project Hub — org-scoped Feishu collaboration and confined Agent runtime. Semantics pinned by docs/adr/ (ADR-0001 through ADR-0027).",
   "scripts": {
     "dev": "npm run prisma:migrate && tsx watch src/server.ts",
-    "build": "tsc -p tsconfig.json && npm run admin:build",
+    "build": "tsc -p tsconfig.json && npm run admin:build && npm run database:build",
     "start": "npm run prisma:migrate && node dist/server.js",
     "check": "tsc -p tsconfig.json --noEmit",
     "audit:production": "npm audit --omit=dev --audit-level=high",
@@ -48,6 +48,8 @@
     "test": "vitest run",
     "test:watch": "vitest",
     "admin:dev": "npm run dev --prefix admin-web",
-    "admin:build": "npm run build --prefix admin-web"
+    "admin:build": "npm run build --prefix admin-web",
+    "database:dev": "npm run dev --prefix database-admin",
+    "database:build": "npm run build --prefix database-admin"
   }
 }