Upgrade to Gradle 9.4.1, AGP 9.1.0, Kotlin 2.3.20

- Gradle wrapper 8.14.2 -> 9.4.1
- AGP 8.10.1 -> 9.1.0 (built-in Kotlin, no separate kotlin.android plugin)
- Kotlin 2.1.20 -> 2.3.20
- KSP 2.1.20-1.0.32 -> 2.3.6 (new versioning scheme)
- settings.gradle.kts: removed @Suppress for dependencyResolutionManagement
- gradle.properties: added android.disallowKotlinSourceSets=false for KSP compat

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/build.gradle.kts

@@ -1,6 +1,5 @@
 plugins {
     alias(libs.plugins.android.application)
-    alias(libs.plugins.kotlin.android)
     alias(libs.plugins.kotlin.compose)
     alias(libs.plugins.ksp)
 }
@@ -42,8 +41,6 @@ android {
         warningsAsErrors = true
         abortOnError = true
         checkDependencies = true
-        // AGP 9.x requires Gradle 9.x; suppress until we're ready to migrate
-        disable += "AndroidGradlePluginVersion"
     }
 }
 

build.gradle.kts

@@ -1,6 +1,5 @@
 plugins {
     alias(libs.plugins.android.application) apply false
-    alias(libs.plugins.kotlin.android) apply false
     alias(libs.plugins.kotlin.compose) apply false
     alias(libs.plugins.ksp) apply false
 }

gradle.properties

@@ -2,3 +2,4 @@ org.gradle.jvmargs=-Xmx2048m -Dfile.encoding=UTF-8
 android.useAndroidX=true
 kotlin.code.style=official
 android.nonTransitiveRClass=true
+android.disallowKotlinSourceSets=false

gradle/libs.versions.toml

@@ -1,7 +1,7 @@
 [versions]
-agp = "8.10.1"
-kotlin = "2.1.20"
-ksp = "2.1.20-1.0.32"
+agp = "9.1.0"
+kotlin = "2.3.20"
+ksp = "2.3.6"
 compose-bom = "2026.03.00"
 room = "2.8.4"
 navigation = "2.9.7"

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.14.2-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-9.4.1-bin.zip
 networkTimeout=10000
 validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME

settings.gradle.kts

@@ -10,7 +10,6 @@ plugins {
     id("org.gradle.toolchains.foojay-resolver-convention") version "1.0.0"
 }
 
-@Suppress("UnstableApiUsage")
 dependencyResolutionManagement {
     repositoriesMode.set(RepositoriesMode.FAIL_ON_PROJECT_REPOS)
     repositories {