CodeIgniter 3 to 4 + PHP 8.4 Upgrade

Upgrade CodeIgniter 3.1.9 Project to CodeIgniter 4 + PHP 8.4 Compatibility

I have a working web application built using CodeIgniter 3.1.9 and PHP 7.4. I want to upgrade it to the latest standards:

• Upgrade CodeIgniter from 3.1.9 to CodeIgniter 4.x (latest stable version)
• Upgrade the backend to PHP 8.4 compatibility
• Refactor existing controllers, models, views, and routes to follow CI4 structure (namespaces, autoloading, etc.)
• Maintain existing API functionality as it is used by an Android mobile app
• Ensure all responses and endpoint structures remain backward compatible
• Fix any deprecated functions or compatibility issues during the transition
• Full testing after migration to ensure smooth functionality

Ideal Developer:
- Has prior experience upgrading CodeIgniter 3 to 4
- Familiar with PHP 8.x deprecations and improvements
- Can work independently and deliver a tested, clean migration
- Bonus: Understands how Android apps consume REST APIs

Deliverables:
- Fully working CodeIgniter 4 project
- Compatible with PHP 8.4+
- Matching all current features and APIs
- Migration documentation (basic)

Please share links to previous CI3 to CI4 migration work if available. This is a fixed-scope project but open to hourly if justified.