更新工作流配置，添加 QEMU 设置步骤；优化日志信息，明确不允许的仓库提示

.gitea/workflows/release-nightly.yml

@@ -20,6 +20,9 @@ jobs:
               with:
                   fetch-depth: 0 # all history for all branches and tags
 
+            - name: Set up QEMU
+              uses: docker/setup-qemu-action@v3
+
             - name: Set up Docker BuildX
               uses: docker/setup-buildx-action@v3