Use larger CI runner for E2E tests and ensure clean test runs

- Use ubuntu-8-core runner (8 cores/32GB RAM) instead of ubuntu-latest
  to provide more resources for TestContainers-based E2E tests
- Add cleanEndToEndTest before running E2E tests to ensure fresh runs

Co-authored by Claude Code

Author: cer

.github/workflows/build.yml

@@ -12,7 +12,7 @@ on:
 
 jobs:
   build:
-    runs-on: ubuntu-latest
+    runs-on: ubuntu-8-core
 
     steps:
     - name: Checkout code

run-end-to-end-tests-using-test-containers.sh

@@ -7,6 +7,7 @@ echo ""
 
 cd ftgo-end-to-end-tests
 
+./gradlew cleanEndToEndTest
 ./gradlew endToEndTest -PendToEndTestMode=TestContainers "$@"
 
 echo ""