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/deploy/deploy_fleet_release.sh

@@ -82,10 +82,11 @@ REMOTE
   rsync -az --delete \
     --exclude node_modules --exclude dist --exclude .env \
     --exclude admin-web/node_modules --exclude admin-web/build --exclude admin-web/.svelte-kit \
+    --exclude database-admin/node_modules --exclude database-admin/build --exclude database-admin/.svelte-kit \
     -e "ssh ${SSH_OPTS[*]}" \
     "$REPO_ROOT/hub/" "$DEPLOY_USER@$HOST:$HUB_DIR/"
 
-  echo "[fleet] npm ci + build (tsc + admin-web SPA)"
+  echo "[fleet] npm ci + build (tsc + admin-web & database-admin SPAs)"
   ssh "${SSH_OPTS[@]}" "$DEPLOY_USER@$HOST" bash -s <<REMOTE
 set -euo pipefail
 flock /var/lock/cph-hub-release-publish bash -c '
@@ -97,9 +98,11 @@ flock /var/lock/cph-hub-release-publish bash -c '
   cd "$HUB_DIR"
   PUPPETEER_SKIP_DOWNLOAD=1 npm ci
   npm ci --prefix admin-web
+  npm ci --prefix database-admin
   npm run audit:production
   npm run build
   test -f admin-web/build/index.html
+  test -f database-admin/build/index.html
   touch "$RELEASE_DIR/.complete"
 '
 REMOTE