docs: add docker compose pull to deployment steps to prevent stale images

Users downloading a release and running `docker compose up -d` may get
cached old images because Docker doesn't pull by default. This caused
confusion when the UI displayed an older version than the release.

- Add `docker compose pull` before `up -d` in both README and README_CN
- Enable WEKNORA_VERSION in .env.example so users can pin a release tag

Closes #2560

.env.example

@@ -31,7 +31,8 @@
 
 # ========== A1. 镜像版本与构建 ==========
 # WeKnora 镜像版本标签：latest（稳定版）/ main（最新开发版）。
-# WEKNORA_VERSION=latest
+# 镜像版本标签，不指定时默认 latest。升级到指定版本（如 0.7.0）可避免本地缓存旧镜像导致版本不一致
+WEKNORA_VERSION=latest
 # Alpine apk 镜像源（构建 app 镜像用，留空用默认源；国内可设 mirrors.tencent.com 加速）。
 APK_MIRROR_ARG=mirrors.tencent.com
 # docreader 镜像构建时 apt 镜像源（留空用默认源）。

README.md

@@ -209,7 +209,8 @@ See [`cli/README.md`](./cli/README.md) for install + 5-minute quickstart and
 git clone https://github.com/Tencent/WeKnora.git
 cd WeKnora
 cp .env.example .env   # Edit .env as needed, see comments in the file
-docker compose up -d   # Start core services
+docker compose pull     # Pull the latest images
+docker compose up -d    # Start core services
 ```
 
 Once started, visit **http://localhost** to get started.

README_CN.md

@@ -186,7 +186,8 @@
 git clone https://github.com/Tencent/WeKnora.git
 cd WeKnora
 cp .env.example .env   # 按需编辑 .env，详见文件内注释
-docker compose up -d   # 启动核心服务
+docker compose pull     # 拉取最新镜像
+docker compose up -d    # 启动核心服务
 ```
 
 启动成功后访问 **http://localhost** 即可使用。