fix: use explicit $HOME path for Maven mount and add verification

Issue: docker-compose was using ~ which may not expand correctly in CI

Changes:
1. docker-compose.yml: Changed ~/.m2 to ${HOME}/.m2
   - Ensures proper path expansion in GitHub Actions
   - $HOME is /home/runner in GitHub Actions runners

2. Added verification step in workflow:
   - Lists all SNAPSHOT artifacts before tests
   - Shows what's available in Maven local repo
   - Will help diagnose if artifacts aren't being restored correctly

This should ensure the Maven container can access the locally built
3.80.1-SNAPSHOT JARs with our debug logging code.

.github/workflows/spark-integration-tests.yml

@@ -199,10 +199,22 @@ jobs:
         curl -s http://localhost:9333/dir/status | jq '.' || echo "jq not available"
         echo "✓ Volume server registered, volumes will be created on-demand during tests"
 
+    - name: Verify Maven artifacts before tests
+      run: |
+        echo "Verifying Maven artifacts are available in ~/.m2/repository..."
+        echo "Checking for SNAPSHOT artifacts:"
+        find ~/.m2/repository/com/seaweedfs -name "*3.80.1-SNAPSHOT*" 2>/dev/null | sort || echo "No SNAPSHOT artifacts found!"
+        echo ""
+        echo "All seaweedfs JARs:"
+        find ~/.m2/repository/com/seaweedfs -name "*.jar" 2>/dev/null | sort
+        
     - name: Run Spark integration tests in Docker
       working-directory: test/java/spark
       run: |
         echo "Running Spark integration tests in Docker container..."
+        echo "Maven repository path on host: $HOME/.m2"
+        echo "Will be mounted as /root/.m2 in container"
+        echo ""
         echo "Docker networks:"
         docker network ls
         echo "Starting spark-tests container (will start dependencies automatically)..."