Add Detox end-to-end tests for core payment flows

Create comprehensive Detox test cases for Android payment flows:

### Test Cases to Implement:
1. **Payment Normal Flow**
- Successful card payment completion
- Form validation and submission
- Success screen verification

2. **Payment Cancelled Flow**
- User cancels payment mid-flow
- Back button handling
- Proper cleanup and state reset

3. **Payment Failed Flow**
- Invalid card details handling
- Network failure scenarios
- Error message display and retry options

Expected Outcome:
- 3 new test files in detox-tests/
- Tests should run on Android emulator
- Proper assertions for each flow state

Files to Create:
- detox-tests/e2e/android/paymentFlow.test.js
- detox-tests/e2e/android/paymentCancel.test.js
- detox-tests/e2e/android/paymentFailure.test.js

Acceptance Criteria:
- [ ] All tests pass on Android emulator
- [ ] Tests use proper Detox matchers and actions
- [ ] Error scenarios are properly handled
- [ ] Tests are documented with clear descriptions