refactor: manifest回归Release构建产物

- ota/目录删除(manifest是CI构建时动态生成上传)
- App URL改为Release下载路径(releases/download/...)
- 流程: CI build→生成manifest(SHA256动态)→上传Release
- Release #7: v0.1.0-dav-android-7-debug.apk + manifest.json

ota/manifest-beta.json

@@ -1 +0,0 @@
-{"version":"0.1.0","builds":{"android":{"type":"apk","tag":"v0.1.0-dav-android-7","url":"https://git.childish-ghost.com/LukeMackin/Yuzu-GCA/releases/download/v0.1.0-dav-android-7/v0.1.0-dav-android-7-debug.apk","sha256":"6cd6bbfe07e8b86b06bc328b7b08138dfb00defc71c8bcc98fbb256b2153aba6","size":3223411,"channel":"beta"}}}

ota/manifest-nightly.json

@@ -1 +0,0 @@
-{"version":"0.1.0","builds":{"android":{"type":"apk","tag":"v0.1.0-dav-android-7","url":"https://git.childish-ghost.com/LukeMackin/Yuzu-GCA/releases/download/v0.1.0-dav-android-7/v0.1.0-dav-android-7-debug.apk","sha256":"6cd6bbfe07e8b86b06bc328b7b08138dfb00defc71c8bcc98fbb256b2153aba6","size":3223411,"channel":"nightly"}}}

ota/manifest.json

@@ -1,14 +0,0 @@
-{
-  "version": "0.1.0",
-  "builds": {
-    "android": {
-      "type": "apk",
-      "tag": "v0.1.0-dav-android-7",
-      "url": "https://git.childish-ghost.com/LukeMackin/Yuzu-GCA/releases/download/v0.1.0-dav-android-7/v0.1.0-dav-android-7-debug.apk",
-      "sha256": "6cd6bbfe07e8b86b06bc328b7b08138dfb00defc71c8bcc98fbb256b2153aba6",
-      "size": 3223411,
-      "channel": "stable",
-      "minVersion": "0.1.0"
-    }
-  }
-}