feat(android): bootstrap native Android module — Gradle + version catalog

M8 phase 1.1: empty multi-project Gradle scaffold (root + :app
placeholder). Version catalog establishes pinned Kotlin/AGP/Compose/
Hilt/Room/Media3/etc. versions for the whole module.

Gradle wrapper (8.10) reused from flutter_client/ — the wrapper jar
is a bootstrap and respects distributionUrl from gradle-wrapper.properties.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

android/gradle.properties

@@ -0,0 +1,7 @@
+org.gradle.jvmargs=-Xmx4g -Dfile.encoding=UTF-8
+org.gradle.parallel=true
+org.gradle.caching=true
+org.gradle.configuration-cache=true
+android.useAndroidX=true
+android.nonTransitiveRClass=true
+kotlin.code.style=official