Split back-office into standalone memind_adm service

Carve the platform super-admin API (/admin-api) and plaza operations console
API (/api/ops/v1) out of the public server.mjs into their own process, so the
user-facing fleet can no longer be taken down or scaled by back-office traffic.

Architecture (split-ready, single process for now):
- admin-routes.mjs: createAdminApi / createOpsApi route factories (DI, single
  source of truth; the route logic moved verbatim out of server.mjs).
- admin-bootstrap.mjs: lean service container (user-auth, LLM providers, minimal
  plaza graph) with no user-facing daemons.
- admin-server.mjs: standalone entry with a console registry. ADMIN_CONSOLES
  selects which consoles a process mounts (default both), so splitting into two
  processes later is a config change, not a code change.
- admin-guard.mjs (+ tests): per-console host / IP-CIDR allowlists, letting the
  super-admin surface be locked down harder than moderation.

server.mjs no longer serves or mounts either surface. user-auth.mjs gains
pagination on listUsers/listUsageRecords/listBillingLedger to back the admin
dashboards. dev.mjs launches memind_adm; the ops SPA proxies /api to it while
/auth stays on the portal. Sessions are read from the shared cookie
(H5_COOKIE_DOMAIN=.tkmind.cn); login stays on the main domain.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

package.json

@@ -18,6 +18,7 @@
     "setup:plaza-tls": "node scripts/plaza-local-tls.mjs",
     "dev:vite": "vite",
     "dev:server": "node server.mjs",
+    "dev:adm": "node admin-server.mjs",
     "dev:plaza-express": "node plaza-server.mjs",
     "dev:ops": "cd ops && npm run dev",
     "ops:grant": "node scripts/grant-ops-role.mjs",
@@ -25,7 +26,7 @@
     "seed:plaza-covers": "node scripts/seed-plaza-covers.mjs",
     "enrich:plaza": "node scripts/enrich-plaza-posts.mjs",
     "build": "vite build",
-    "test": "node --test auth.test.mjs asr-proxy.test.mjs billing.test.mjs billing-recharge.test.mjs wechat-pay.test.mjs wechat-oauth.test.mjs capabilities.test.mjs policies.test.mjs chat-skills.test.mjs user-publish.test.mjs user-memory-profile.test.mjs skills-registry.test.mjs mindspace.test.mjs mindspace-scan.test.mjs mindspace-assets.test.mjs mindspace-pages.test.mjs mindspace-publications.test.mjs mindspace-chat-save.test.mjs mindspace-chat-context.test.mjs mindspace-content-scan.test.mjs mindspace-html-localize.test.mjs mindspace-visual-editor.test.mjs mindspace-cleanup.test.mjs mindspace-thumbnails.test.mjs mindspace-workspace-thumbnails.test.mjs mindspace-workspace-sync.test.mjs mindspace-asset-preview.test.mjs mindspace-agent-jobs.test.mjs mindspace-agent-runner.test.mjs message-stream.test.mjs plaza-posts.test.mjs plaza-interactions.test.mjs plaza-algorithm.test.mjs plaza-seo.test.mjs plaza-ops.test.mjs user-auth.test.mjs llm-providers.test.mjs",
+    "test": "node --test auth.test.mjs asr-proxy.test.mjs billing.test.mjs billing-recharge.test.mjs wechat-pay.test.mjs wechat-oauth.test.mjs capabilities.test.mjs policies.test.mjs chat-skills.test.mjs user-publish.test.mjs user-memory-profile.test.mjs skills-registry.test.mjs mindspace.test.mjs mindspace-scan.test.mjs mindspace-assets.test.mjs mindspace-pages.test.mjs mindspace-publications.test.mjs mindspace-chat-save.test.mjs mindspace-chat-context.test.mjs mindspace-content-scan.test.mjs mindspace-html-localize.test.mjs mindspace-visual-editor.test.mjs mindspace-cleanup.test.mjs mindspace-thumbnails.test.mjs mindspace-workspace-thumbnails.test.mjs mindspace-workspace-sync.test.mjs mindspace-asset-preview.test.mjs mindspace-agent-jobs.test.mjs mindspace-agent-runner.test.mjs message-stream.test.mjs plaza-posts.test.mjs plaza-interactions.test.mjs plaza-algorithm.test.mjs plaza-seo.test.mjs plaza-ops.test.mjs user-auth.test.mjs llm-providers.test.mjs admin-guard.test.mjs",
     "test:mindspace-e2e": "node scripts/mindspace-e2e.mjs",
     "test:mindspace-pages-e2e": "node scripts/mindspace-pages-e2e.mjs",
     "test:mindspace-publications-e2e": "node scripts/mindspace-publications-e2e.mjs",