feat(polaris)!: 改为 standalone 容器运行

将 Next.js 构建切换为 standalone，新增多阶段 Docker 镜像和非 root 运行。
CI 改为启动服务检查页面与静态资源，并移除静态导出校验。

BREAKING CHANGE: 不再生成 out/ 静态产物，部署需运行 Node 服务容器。

.gitea/workflows/polaris-ci.yml

@@ -32,8 +32,38 @@ jobs:
       - name: Test
         run: corepack pnpm test
 
-      - name: Build static export
+      - name: Build standalone server
         run: corepack pnpm build
 
-      - name: Verify static export
-        run: corepack pnpm verify:export
+      - name: Prepare standalone output
+        run: |
+          test -f .next/standalone/server.js
+          cp -r public .next/standalone/
+          cp -r .next/static .next/standalone/.next/
+
+      - name: Smoke test standalone server
+        shell: bash
+        run: |
+          set -euo pipefail
+          base_url="http://127.0.0.1:3100"
+          PORT=3100 HOSTNAME=127.0.0.1 node .next/standalone/server.js &
+          server_pid=$!
+          trap 'kill "$server_pid" 2>/dev/null || true' EXIT
+
+          ready=0
+          for _ in $(seq 1 30); do
+            if curl -fsS -o /dev/null "$base_url/"; then
+              ready=1
+              break
+            fi
+            kill -0 "$server_pid" 2>/dev/null || { echo "server process exited early" >&2; exit 1; }
+            sleep 1
+          done
+          test "$ready" -eq 1 || { echo "server not ready within 30s" >&2; exit 1; }
+
+          curl -fsS -o /dev/null "$base_url/categories/dev/"
+          curl -fsS -o /dev/null "$base_url/brand/logo.svg"
+
+          static_asset=$(curl -fsS "$base_url/" | grep -o '/_next/static/[^"]*' | sed -n '1p')
+          test -n "$static_asset" || { echo "homepage references no /_next/static asset" >&2; exit 1; }
+          curl -fsS -o /dev/null "$base_url$static_asset"