🐛 fix: Fix GitHub workflow build failures

- Fixed compileSdk syntax error in build.gradle.kts (was using incorrect 'compileSdk { version = release(36) }' instead of 'compileSdk = 36')
- Moved splits configuration out of defaultConfig to correct location
- Added comprehensive ProGuard rules to handle OkHttp's optional dependencies (BouncyCastle, Conscrypt, OpenJSSE)
- Added ProGuard rules for Sardine WebDAV, Coroutines, and Gson
- Build now completes successfully both locally and in CI/CD

android/app/proguard-rules.pro

@@ -18,4 +18,46 @@
 
 # If you keep the line number information, uncomment this to
 # hide the original source file name.
-#-renamesourcefileattribute SourceFile
+#-renamesourcefileattribute SourceFile
+
+# OkHttp platform-specific SSL classes (optional dependencies)
+# These are platform-specific implementations that OkHttp uses optionally
+# We don't need them for Android, so we ignore warnings about missing classes
+-dontwarn org.bouncycastle.jsse.BCSSLParameters
+-dontwarn org.bouncycastle.jsse.BCSSLSocket
+-dontwarn org.bouncycastle.jsse.provider.BouncyCastleJsseProvider
+-dontwarn org.conscrypt.Conscrypt$Version
+-dontwarn org.conscrypt.Conscrypt
+-dontwarn org.conscrypt.ConscryptHostnameVerifier
+-dontwarn org.openjsse.javax.net.ssl.SSLParameters
+-dontwarn org.openjsse.javax.net.ssl.SSLSocket
+-dontwarn org.openjsse.net.ssl.OpenJSSE
+
+# Sardine WebDAV library
+-keep class com.thegrizzlylabs.sardineandroid.** { *; }
+-dontwarn org.w3c.dom.ElementTraversal
+
+# Keep WebDAV related classes
+-keepclassmembers class * {
+    @com.thegrizzlylabs.sardineandroid.* *;
+}
+
+# Coroutines
+-keepnames class kotlinx.coroutines.internal.MainDispatcherFactory {}
+-keepnames class kotlinx.coroutines.CoroutineExceptionHandler {}
+-keepclassmembers class kotlinx.** {
+    volatile <fields>;
+}
+
+# Gson
+-keepattributes Signature
+-keepattributes *Annotation*
+-dontwarn sun.misc.**
+-keep class com.google.gson.** { *; }
+-keep class * implements com.google.gson.TypeAdapter
+-keep class * implements com.google.gson.TypeAdapterFactory
+-keep class * implements com.google.gson.JsonSerializer
+-keep class * implements com.google.gson.JsonDeserializer
+
+# Keep your app's data classes
+-keep class dev.dettmer.simplenotes.** { *; }