统一维护与错误页面并修复移动端顶部文案

新增品牌维护页和404页面并补齐网关路由
将临时维护公告迁到release外运行态覆盖并增加构建门禁
同步Nginx、Pingora、部署脚本与生产运维文档
隐藏移动端顶部SEO介绍并保留桌面端与H1语义
增加维护页、404页和移动端回归测试

package.json

@@ -32,6 +32,7 @@
     "check:encoding": "node scripts/check-encoding.mjs",
     "check:spacetime-schema": "node scripts/check-spacetime-schema-guard.mjs",
     "check:production-ops": "node scripts/check-production-ops-guardrails.mjs",
+    "check:maintenance-page": "node scripts/check-maintenance-page.mjs",
     "check:database-backup": "node scripts/check-database-backup-to-oss.mjs",
     "check:production-health-patrol": "node scripts/check-production-health-patrol.mjs",
     "check:production-health-patrol-env": "node scripts/check-production-health-patrol-env-check.mjs",
@@ -82,7 +83,7 @@
     "lint:guardrails": "npm run lint:eslint",
     "typecheck": "tsc -p tsconfig.typecheck-guardrails.json --noEmit",
     "typecheck:guardrails": "npm run typecheck",
-    "lint": "npm run check:encoding && npm run check:spacetime-schema && npm run check:production-ops && npm run lint:eslint && npm run typecheck",
+    "lint": "npm run check:encoding && npm run check:spacetime-schema && npm run check:production-ops && npm run check:maintenance-page && npm run lint:eslint && npm run typecheck",
     "lint:fix": "eslint . --ext .ts,.tsx,.js,.mjs,.cjs --fix && prettier --write .",
     "format": "prettier --write .",
     "format:check": "prettier --check .",