feat: adopt proven Flutter BrowserStack pattern from PR #134

Major simplification following the working pattern from PR #134:

**Eliminated Complex Appium/Python Approach**:
- Remove Python scripts and Appium dependencies
- Remove complex multi-job Android/iOS/Web structure
- No more Python environment management issues

**New Simple & Proven Pattern**:
- **Job 1**: Build APK + Upload to BrowserStack for manual testing
- **Job 2**: Run integration tests locally with Android emulator
- **Project Name**: "Ditto Flutter" (matches proven pattern)
- **Focus**: BrowserStack for manual testing, local for automation

**Key Benefits**:
- No Python dependencies or environment issues
- Follows working pattern from successful PR #134
- Clean separation: BrowserStack upload vs. local testing
- Proper Flutter-native integration testing with flutter drive
- Much simpler and more maintainable

**BrowserStack Usage**:
- Upload APK to "Ditto Flutter" project for manual testing
- Manual testing via BrowserStack App Live
- Automated testing via local Android emulator

This approach is proven to work and eliminates all the complexity!

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: teodorciuraru