fix: revert R8 minification for release builds (added by 5ad3cb1)

Commit 5ad3cb1 added isMinifyEnabled/isShrinkResources/proguardFiles to
the release buildType, enabling R8 on the Android-native side. Without
comprehensive keep rules, R8 stripped plugin classes accessed reflectively
at launch (flutter_foreground_task, android_package_installer, shizuku,
etc. — 267 classes in usage.txt), causing an immediate
NoClassDefFoundError crash in production. Reverting to standard Flutter
defaults (no Android-native minification) to restore working release
builds.

android/app/build.gradle.kts

@@ -77,12 +77,6 @@ android {
 
     buildTypes {
         getByName("release") {
-            isMinifyEnabled = true
-            isShrinkResources = true
-            proguardFiles(
-                getDefaultProguardFile("proguard-android-optimize.txt"),
-                "proguard-rules.pro",
-            )
             val releaseSigningConfig = signingConfigs.getByName("release")
             signingConfig = if (keystorePropertiesExists && releaseSigningConfig.storeFile != null) {
                 releaseSigningConfig