fix(build): baseline configuration and proxy setup

- Downgrade AGP 9.0.0 -> 8.9.2, Kotlin 2.2.10 -> 2.1.20, KSP and Compose Multiplatform to compatible versions.
- Switch Gradle wrapper to 8.13 (8.11.1 download unavailable, 9.5.1 incompatible with AGP 8.9).
- Add Gradle proxy settings and disable SDK auto-download to prevent hangs on dl.google.com.
- Remove generated gradle-daemon-jvm.properties causing JetBrains JDK lookup failure.
- Fix JvmVendorSpec.ANY incompatibility on the new toolchain.
- Temporarily disable externalNativeBuild until NDK 27.0.12077973 is installed.
- Baseline ':app:tasks' now passes.

shared/build.gradle.kts

@@ -31,7 +31,9 @@ kotlin {
         androidTarget()
     }
     jvm("desktop")
-    jvmToolchain(21)
+    jvmToolchain {
+        languageVersion.set(JavaLanguageVersion.of(21))
+    }
 
     sourceSets {
         val commonMain by getting