Bump AGP to 8.5.2 and Gradle to 8.7 for 16 KB page-size support

Every .so this project builds was already ELF-segment-aligned for 16 KB
pages (build-image/Dockerfile's ANDROID_16KB_LDFLAGS, app/build.gradle's
own CMAKE_SHARED_LINKER_FLAGS), but AGP 8.1.1 doesn't align native
libraries' zip entries within the APK itself - that only became automatic
in AGP 8.5.1, which is what Android Studio's "not compatible with 16 KB
devices" warning was actually flagging. No build-image changes needed:
Gradle/AGP are resolved over the network at build time, not baked into
the image.

android/build.gradle

@@ -9,7 +9,18 @@ buildscript {
         google()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:8.1.1'
+        // 8.5.1+ needed for AGP to automatically 16 KB-align native
+        // libraries' zip entries within the APK - the actual .so's are
+        // already ELF-segment-aligned for this regardless of AGP version
+        // (see build-image/Dockerfile's ANDROID_16KB_LDFLAGS and
+        // app/build.gradle's own CMAKE_SHARED_LINKER_FLAGS), but that alone
+        // doesn't get them 16 KB-aligned *within the APK's zip*, which is
+        // what Android Studio's "not compatible with 16 KB devices"
+        // warning is actually about. Needs Gradle 8.7+ (see
+        // gradle/wrapper/gradle-wrapper.properties) and JDK 17 in whatever
+        // runs gradlew (already the case - see build-image/Dockerfile's
+        // openjdk-17-jdk-headless).
+        classpath 'com.android.tools.build:gradle:8.5.2'
     }
 }