feat(admin): apix-admin UI at admin.api-index.org

Internal maintainer dashboard: global stats, sandbox list with
tier-filter and pagination, sandbox drill-down with D3 world map,
tier-promotion form. API-key auth via HttpOnly cookie. Port 8084,
rolling a/b deploy alongside the existing service pairs.

- apix-common: AdminSandboxSummary, AdminSandboxListResponse, AdminStatsResponse DTOs
- apix-registry: AdminResource (4 endpoints), SandboxService.listAllSandboxes + getGlobalStats
- apix-registry: SandboxResource GET /{uuid}/dashboard endpoint (was missing — fixes portal 500)
- apix-portal: RegistryClient path corrected to /dashboard
- apix-admin: new Quarkus module — auth filter, registry REST client, 3 resources, 6 Qute templates, admin.js
- infra: Dockerfile.admin, docker-compose admin-a/b services, Caddyfile admin.api-index.org block
- scripts: deploy-bluegreen.sh extended for admin-a/b

Co-Authored-By: Mira Rehfeld <noreply@anthropic.com>

scripts/restart.sh

@@ -13,6 +13,9 @@ TARGET="${1:-all}"
 GREEN='\033[0;32m'; NC='\033[0m'
 info() { echo -e "${GREEN}[apix]${NC} $*"; }
 
+_on_exit() { echo ""; read -rp "Press Enter to close…" _; }
+trap _on_exit EXIT
+
 # ── tmux mode ────────────────────────────────────────────────────────────────
 if command -v tmux &>/dev/null && tmux has-session -t apix-dev 2>/dev/null; then
   _restart_window() {