Optimize GitLab CI cache to fix disk space issues

- Reduce cached paths: only cache wrapper and modules-2 (not transforms)
- Remove android/.gradle/ and build/ from cache (too large)
- Add before_script cleanup of transform caches and lock files
- Add 'gradle clean' before build to ensure fresh build
- Set explicit cache policy: pull-push
- Fixes 'no space left on device' errors in GitLab runners

Cache size reduced from ~2-3GB to ~200MB

.gitlab-ci.yml

@@ -11,20 +11,24 @@ variables:
 cache:
   key: ${CI_COMMIT_REF_SLUG}
   paths:
-    - .gradle/
+    - .gradle/wrapper
+    - .gradle/caches/modules-2
     - .pub-cache/
-    - android/.gradle/
-    - build/
+  policy: pull-push
 
 build:torrent-engine:
   stage: build
   image: mingc/android-build-box:latest
   before_script:
     - echo "sdk.dir=${ANDROID_SDK_ROOT:-/opt/android-sdk}" > android/local.properties
+    # Clean up old Gradle cache to free space
+    - rm -rf .gradle/caches/transforms-*
+    - rm -rf .gradle/caches/*/transforms
+    - find .gradle/caches -name "*.lock" -type f -delete || true
   script:
     - cd android
     - chmod +x gradlew
-    - ./gradlew :torrentengine:assembleRelease --no-daemon --stacktrace
+    - ./gradlew clean :torrentengine:assembleRelease --no-daemon --stacktrace
   artifacts:
     paths:
       - android/torrentengine/build/outputs/aar/*.aar