build: switch apply(from) to Groovy publish.gradle for AGP compat

KTS scripts loaded via apply(from) are compiled without AGP on the
classpath, so LibraryExtension and ext are unresolvable. Groovy
applied scripts are evaluated dynamically and don't have this issue.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

gradle/publish.gradle

@@ -0,0 +1,23 @@
+apply plugin: 'maven-publish'
+
+afterEvaluate {
+    publishing {
+        publications {
+            release(MavenPublication) {
+                from components.release
+                groupId rootProject.group
+                artifactId project.name
+                version rootProject.version
+            }
+        }
+        repositories {
+            maven {
+                url rootProject.ext['nexusUrl']
+                credentials {
+                    username rootProject.ext['nexusUser']
+                    password rootProject.ext['nexusPassword']
+                }
+            }
+        }
+    }
+}

sdk-core/build.gradle.kts

@@ -4,7 +4,7 @@ plugins {
     alias(libs.plugins.kotlin.serialization)
 }
 
-apply(from = rootProject.file("gradle/publish.gradle.kts"))
+apply(from = rootProject.file("gradle/publish.gradle"))
 
 android {
     namespace = "com.xuqm.sdk.core"

sdk-im/build.gradle.kts

@@ -2,7 +2,7 @@ plugins {
     alias(libs.plugins.android.library)
 }
 
-apply(from = rootProject.file("gradle/publish.gradle.kts"))
+apply(from = rootProject.file("gradle/publish.gradle"))
 
 android {
     namespace = "com.xuqm.sdk.im"

sdk-push/build.gradle.kts

@@ -2,7 +2,7 @@ plugins {
     alias(libs.plugins.android.library)
 }
 
-apply(from = rootProject.file("gradle/publish.gradle.kts"))
+apply(from = rootProject.file("gradle/publish.gradle"))
 
 android {
     namespace = "com.xuqm.sdk.push"

sdk-update/build.gradle.kts

@@ -2,7 +2,7 @@ plugins {
     alias(libs.plugins.android.library)
 }
 
-apply(from = rootProject.file("gradle/publish.gradle.kts"))
+apply(from = rootProject.file("gradle/publish.gradle"))
 
 android {
     namespace = "com.xuqm.sdk.update"