feat: 添加版本更新检查功能

- 后端新增 /api/admin/system/check-update 接口，从 GitHub Tags 获取最新版本
- 前端新增 UpdateDialog 组件，管理员登录后自动检查更新并弹窗提示
- 同一会话内只检查一次，点击"稍后提醒"后 24 小时内不再提示
- CI 和 deploy.sh 自动生成 _version.py 版本文件

.github/workflows/docker-publish.yml

@@ -146,10 +146,33 @@ jobs:
             type=semver,pattern={{major}}.{{minor}}
             type=sha,prefix=
 
+      - name: Extract version from tag
+        id: version
+        run: |
+          # 从 tag 提取版本号，如 v0.2.5 -> 0.2.5
+          VERSION="${GITHUB_REF#refs/tags/v}"
+          if [ "$VERSION" = "$GITHUB_REF" ]; then
+            # 不是 tag 触发，使用 git describe
+            VERSION=$(git describe --tags --always | sed 's/^v//')
+          fi
+          echo "version=$VERSION" >> $GITHUB_OUTPUT
+          echo "Extracted version: $VERSION"
+
       - name: Update Dockerfile.app to use registry base image
         run: |
           sed -i "s|FROM aether-base:latest AS builder|FROM ${{ env.REGISTRY }}/${{ env.BASE_IMAGE_NAME }}:latest AS builder|g" Dockerfile.app
 
+      - name: Generate version file
+        run: |
+          # 生成 _version.py 文件
+          cat > src/_version.py << EOF
+          # Auto-generated by CI
+          __version__ = '${{ steps.version.outputs.version }}'
+          __version_tuple__ = tuple(int(x) for x in '${{ steps.version.outputs.version }}'.split('.') if x.isdigit())
+          version = __version__
+          version_tuple = __version_tuple__
+          EOF
+
       - name: Build and push app image
         uses: docker/build-push-action@v5
         with: