fix(ci): 调整流水线步骤顺序，composer install 移至 php think 命令之前

checkout 后没有 vendor 目录，导致 php think admin:stack:mode 报错。
将 composer install 抽为独立步骤并提前执行，确保 php think 命令可正常运行。

source/stack/default/.gitea/workflows/build-and-deploy.yml

@@ -22,10 +22,6 @@ jobs:
         with:
           fetch-depth: 1
 
-      - name: 切换到 docker-serve 模式
-        shell: bash
-        run: php think admin:stack:mode use docker-serve -f
-
       - name: 生成 .env
         shell: bash
         env:
@@ -55,6 +51,17 @@ jobs:
 
           mv .env.tmp .env
 
+      - name: 安装依赖
+        shell: bash
+        run: |
+          set -euo pipefail
+          composer config -g repos.packagist composer https://nexus.hl7.top:1243/repository/composer-proxy/
+          composer install --no-dev --no-interaction --prefer-dist --optimize-autoloader
+
+      - name: 切换到 docker-serve 模式
+        shell: bash
+        run: php think admin:stack:mode use docker-serve -f
+
       - name: 打包发布文件
         shell: bash
         env:
@@ -62,9 +69,6 @@ jobs:
         run: |
           set -euo pipefail
 
-          composer config -g repos.packagist composer https://nexus.hl7.top:1243/repository/composer-proxy/
-          composer install --no-dev --no-interaction --prefer-dist --optimize-autoloader
-
           TMP_PACKAGE="/tmp/${PACKAGE_NAME}"
           rm -f "$TMP_PACKAGE" "$PACKAGE_NAME"