Add project metadata and Gradle wrapper

- PLAN.md: architecture design document
- .idea/: Android Studio project configuration
- Gradle wrapper: v9.4.1 with daemon JVM properties

Co-Authored-By: Claude Opus 4.6 (1M context)

Signed-off-by: Avinal Kumar <avinal.xlvii@gmail.com>

.idea/vcs.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="VcsDirectoryMappings">
+    <mapping directory="$PROJECT_DIR$" vcs="Git" />
+  </component>
+</project>