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.

test/integration/ci_environment_test.dart

@@ -0,0 +1,83 @@
+import 'dart:io';
+
+import 'package:flutter_test/flutter_test.dart';
+
+void main() {
+  group('CI Environment Tests', () {
+    test('should detect GitHub Actions environment', () {
+      final isGitHubActions = Platform.environment['GITHUB_ACTIONS'] == 'true';
+      final isCI = Platform.environment['CI'] == 'true';
+      final runnerOS = Platform.environment['RUNNER_OS'];
+      
+      print('Environment Variables:');
+      print('  GITHUB_ACTIONS: ${Platform.environment['GITHUB_ACTIONS']}');
+      print('  CI: ${Platform.environment['CI']}');
+      print('  RUNNER_OS: $runnerOS');
+      print('  Platform: ${Platform.operatingSystem}');
+      
+      if (isGitHubActions || isCI) {
+        print('✅ Running in CI/GitHub Actions environment');
+        expect(isCI, isTrue, reason: 'CI environment variable should be set');
+        
+        if (isGitHubActions) {
+          expect(runnerOS, isNotNull, reason: 'RUNNER_OS should be set in GitHub Actions');
+          print('  GitHub Actions Runner OS: $runnerOS');
+        }
+      } else {
+        print('🔧 Running in local development environment');
+      }
+      
+      // Test should always pass regardless of environment
+      expect(Platform.operatingSystem, isNotEmpty);
+    });
+
+    test('should have correct Dart/Flutter environment in CI', () {
+      final dartVersion = Platform.version;
+      print('Dart version: $dartVersion');
+      
+      // In CI, we should have Dart available
+      expect(dartVersion, isNotEmpty);
+      expect(dartVersion, contains('Dart'));
+      
+      // Check if running in CI and validate expected environment
+      final isCI = Platform.environment['CI'] == 'true';
+      if (isCI) {
+        print('✅ Dart environment validated in CI');
+        
+        // CI should have these basic characteristics
+        expect(Platform.operatingSystem, anyOf('linux', 'macos', 'windows'));
+        
+        // GitHub Actions typically runs on Linux
+        final runnerOS = Platform.environment['RUNNER_OS'];
+        if (runnerOS == 'Linux') {
+          expect(Platform.operatingSystem, 'linux');
+        }
+      }
+    });
+
+    test('should handle network connectivity gracefully', () async {
+      // Simple network test that won't fail in restricted environments
+      try {
+        // Test with a reliable endpoint
+        final socket = await Socket.connect('8.8.8.8', 53, timeout: const Duration(seconds: 5));
+        socket.destroy();
+        print('✅ Network connectivity available');
+      } catch (e) {
+        print('ℹ️ Limited network connectivity: $e');
+        // Don't fail the test - some CI environments have restricted network
+      }
+      
+      // Test should always pass
+      expect(true, isTrue);
+    });
+
+    test('should validate test infrastructure', () {
+      // Basic test framework validation
+      expect(testWidgets, isNotNull, reason: 'Flutter test framework should be available');
+      expect(setUp, isNotNull, reason: 'Test setup functions should be available');
+      expect(tearDown, isNotNull, reason: 'Test teardown functions should be available');
+      
+      print('✅ Test infrastructure validated');
+    });
+  });
+}