fix: migrate jvmTarget to compilerOptions DSL for Kotlin 2.x (#352)

## Summary

- `android/app/build.gradle.kts` used `kotlinOptions { jvmTarget = JavaVersion.VERSION_17.toString() }`, which Kotlin 2.x treats as a compilation error ("Using jvmTarget: String is an error")
- Replaced with the `compilerOptions` DSL using `org.jetbrains.kotlin.gradle.dsl.JvmTarget.JVM_17`

## Test plan

- [x] Confirmed root cause from CI run #1316 logs: `e: .../build.gradle.kts:20:9: Using 'jvmTarget: String' is an error`
- [ ] CI deploy workflow should now pass the Android bundle build step

Closes #351

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Co-authored-by: Thomas SharedInbox <sharedinbox@thomas-guettler.de>
Reviewed-on: https://codeberg.org/guettli/sharedinbox/pulls/352

android/app/build.gradle.kts

@@ -16,8 +16,10 @@ android {
         isCoreLibraryDesugaringEnabled = true
     }
 
-    kotlinOptions {
-        jvmTarget = JavaVersion.VERSION_17.toString()
+    kotlin {
+        compilerOptions {
+            jvmTarget = org.jetbrains.kotlin.gradle.dsl.JvmTarget.JVM_17
+        }
     }
 
     signingConfigs {