fix(build): add missing gradle-kotlin-dsl import to the core domain convention plugin

The iOS CI run failed in both jobs before reaching any product code: the
convention plugin itself did not compile. CoreDomainPlugin.kt used the
reified extensions.configure<KotlinMultiplatformExtension> { } form, but
unlike every other plugin in this directory it was missing the
org.gradle.kotlin.dsl.configure import. Without it only the member
overloads taking an explicit type parameter resolve, so the extension
receiver cannot be inferred and all twenty subsequent unresolved
references - jvmToolchain, jvm(), iosArm64(), binaries.framework,
sourceSets with the commonMain/commonTest/jvmTest accessors - are one
cascading failure, not twenty bugs.

build-logic is the first thing both CI jobs compile, and it has never
been compiled anywhere before this run, so the workflow is doing exactly
what it was added for: catching what no local machine can check.

build-logic/convention/src/main/java/com/rtbishop/look4sat/convention/CoreDomainPlugin.kt

@@ -19,6 +19,7 @@ package com.rtbishop.look4sat.convention
 
 import org.gradle.api.Plugin
 import org.gradle.api.Project
+import org.gradle.kotlin.dsl.configure
 import org.jetbrains.kotlin.gradle.dsl.KotlinMultiplatformExtension
 
 /**