Refactor Gitea production deployment process to utilize SSH for remote operations

- Updated deployment specification to reflect the new architecture involving servers A, B, and C.
- Revised README to describe the new deployment method using Gitea Runner and SSH.
- Modified `compose.production.yaml` to remove build context and use image tags directly.
- Enhanced deployment documentation to clarify configuration steps and environment variable requirements.
- Introduced `deploy-remote.sh` script for handling remote deployment tasks over SSH.
- Added unit tests for deployment scripts to ensure robustness and error handling.
- Updated `deploy-production.sh` to streamline image pulling and deployment processes.

README.md

@@ -90,7 +90,7 @@ Chatbox 来源使用 `kind=chatbox`，会话 ID 为 `reference`，生成轮次 I
 
 ## Gitea 自动部署（复用已有 PostgreSQL）
 
-使用独立的 `compose.production.yaml` 和 `.gitea/workflows/deploy-production.yaml`。配置步骤、数据库账号密码位置及升级处理见 [Gitea 部署说明](docs/deployment-gitea.md)。
+Gitea Runner 构建镜像并推送到服务器 A 的 Gitea Packages，再通过 SSH 到服务器 B 拉取镜像、迁移和部署；B 上的应用通过 `DATABASE_URL` 连接服务器 C 的内网 PostgreSQL。使用独立的 `compose.production.yaml` 和 `.gitea/workflows/deploy-production.yaml`。镜像仓库、SSH、数据库配置及升级处理见 [Gitea 部署说明](docs/deployment-gitea.md)。
 
 ## 公网 HTTPS 部署