feat(admin): integrate Next.js admin panel (admin-next/) from feat/nextjs-admin

- Add admin-next/: full Next.js + Prisma + shadcn admin panel (45 API routes, 76 components)
- docker-compose: tg_shop_admin service (port 3000, shared db/shop.db, prisma), bot talks to it via ADMIN_CHAT_URL=http://tg_shop_admin:3000/api/chat
- tor-proxy now proxies onion admin to tg_shop_admin:3000 (new panel)
- chatbotService: ADMIN_CHAT_URL default = http://tg_shop_admin:3000/api/chat (removed localhost:3100 anachronism)
- .env admin secrets gitignored (admin-next/.env)

admin-next/.dockerignore

@@ -0,0 +1,27 @@
+node_modules
+.next
+.git
+git
+*.md
+db/*.db
+db/*.db-journal
+tool-results/
+agent-ctx/
+.zscripts/
+screenshot-*.png
+keepalive.js
+seed-standalone.ts
+standalone-server.js
+gitea-*.json
+*.log
+dev.log
+server.log
+.env
+.dev
+tests/
+examples/
+mini-services/
+upload/
+download/
+Claude.md
+.claude