feat: Add comprehensive integration tests with real Sintel magnet link for GitHub Actions

Integration Testing Infrastructure:
- Add real magnet link test using Sintel (Creative Commons licensed film)
- Create comprehensive torrent integration tests that work in GitHub Actions
- Add CI environment detection and validation tests
- Enable integration test execution in GitHub Actions workflow

Sintel Integration Test (test/integration/torrent_integration_test.dart):
- Uses official Sintel magnet link from Blender Foundation
- Tests real magnet link parsing and validation
- Covers all torrent operations: add, pause, resume, remove
- Tests file priority management and video file detection
- Includes performance tests and timeout handling
- Validates torrent hash extraction and state management
- Works with mock platform channel (no real downloads)

CI Environment Test (test/integration/ci_environment_test.dart):
- Detects GitHub Actions and CI environments
- Validates Dart/Flutter environment in CI
- Tests network connectivity gracefully
- Verifies test infrastructure availability

GitHub Actions Integration:
- Add integration test step to test.yml workflow
- Set CI and GITHUB_ACTIONS environment variables
- Use --reporter=expanded for detailed test output
- Run after unit tests but before coverage upload

Key Features:
- Mock platform channel prevents real downloads
- Works on any platform (Linux/macOS/Windows)
- Fast execution suitable for CI pipelines
- Uses only open source, legally free content
- Comprehensive error handling and timeouts
- Environment-aware test configuration

Documentation:
- Detailed README for integration tests
- Troubleshooting guide for CI issues
- Explanation of mock vs real testing approach
- Security and licensing considerations

This enables thorough testing of torrent functionality
in GitHub Actions while respecting copyright and
maintaining fast CI execution times.

.github/workflows/test.yml

@@ -60,6 +60,13 @@ jobs:
       - name: Run tests
         run: flutter test --coverage
 
+      - name: Run Integration tests  
+        run: flutter test test/integration/ --reporter=expanded
+        env:
+          # Mark that we're running in CI
+          CI: true
+          GITHUB_ACTIONS: true
+
       - name: Upload coverage to Codecov
         uses: codecov/codecov-action@v4
         with: