feat: manifest字段规范化 {latest,min_version,url,sha256} + v6动态版本对比

- h5_version → latest + min_version(老旧客户端提示需APK升级)
- v6 HTML: 去掉硬编码版本号,动态读取页面ver元素比对
- TBD sha256 → 直接拒绝(非空占位符)
- 域名校验保留

ota/h5/manifest-nightly.json

@@ -1 +1 @@
-{"h5_version":"0.1.0-dav-android-7","h5_sha256":"TBD-v7-not-built","h5_url":"https://git.childish-ghost.com/LukeMackin/Yuzu-GCA/raw/branch/main/ota/h5/index-v7.html"}
+{"url":"https://git.childish-ghost.com/LukeMackin/Yuzu-GCA/raw/branch/main/ota/h5/index-v7.html","min_version":"0.1.0-dav-android-5","latest":"0.1.0-dav-android-7","sha256":"TBD-v7-not-built"}