fix(android): read Kotlin version from root project

- Read kotlinVersion from rootProject.ext instead of hardcoding
- Matches stripe-react-native pattern for version detection
- Ensures Kotlin 2.0 detection works correctly

Author: programmeraditya

packages/stripe_android/android/build.gradle

@@ -2,7 +2,12 @@ group 'com.flutter.stripe'
 version '1.0-SNAPSHOT'
 
 buildscript {
-    ext.kotlin_version = '1.9.0'
+    // Read Kotlin version from root project or fallback to 1.9.0
+    def kotlin_version = rootProject.ext.has('kotlinVersion')
+        ? rootProject.ext.get('kotlinVersion')
+        : '1.9.0'
+
+    ext.kotlin_version = kotlin_version
     ext.stripe_version = '21.26.+'
     ext.compose_version = '1.5.1'
 
@@ -30,6 +35,10 @@ rootProject.allprojects {
     }
 }
 
+// Read Kotlin version from root project or fallback to 1.9.0
+def kotlin_version = rootProject.ext.has('kotlinVersion')
+    ? rootProject.ext.get('kotlinVersion')
+    : '1.9.0'
 def kotlinMajor = kotlin_version.tokenize('\\.')[0].toInteger()
 
 apply plugin: 'com.android.library'