feat: ota/三渠道manifest(固定raw URL)

- ota/manifest-stable.json / beta.json / nightly.json
- App URL改回raw(固定路径,不随版本号变)
- v0.1.0→v0.2.0升级时只需更新JSON内容,URL不变

packages/client-android/android/app/src/main/java/dev/yuzu/gca/MainActivity.kt

@@ -102,7 +102,7 @@ class MainActivity : AppCompatActivity() {
     }
 
     private fun manifestUrl(channel: String): String {
-        val base = "https://git.childish-ghost.com/LukeMackin/Yuzu-GCA/releases/download/v0.1.0-dav-android-7"
+        val base = "https://git.childish-ghost.com/LukeMackin/Yuzu-GCA/raw/branch/main/ota"
         return when (channel) {
             "beta" -> "$base/manifest-beta.json"
             "nightly" -> "$base/manifest-nightly.json"