Release 2.0.0 of Quick UConvert

[Soda Money]

Some pretty meaningful changes in this one. 

As always, grab the update here: https://play.google.com/store/apps/details?id=com.quc.app

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New conversion categories 
- Added 8 entirely new categories: Energy, Mass Flow, Moment, Power, Pressure, Speed, Stiffness, and Volumetric Flow — with full unit sets. This completes the original unit roadmap.

Accuracy overhaul 
- Switched the conversion engine from Double to BigDecimal, eliminating floating-point rounding error on conversions.
- The copy button now copies the full-precision decimal value instead of the rounded display string.

Bug fixes 
- Fixed a naming collision (bit vs Bit) that broke Digital Storage conversions.
- Fixed the category dropdown showing raw internal names instead of the proper display name.
- Removed a redundant category-validity check that no longer served a purpose.

Release infrastructure
- Added Fastlane automation for building and uploading Play Store releases.
- Added Play Store listing assets: hi-res icon, feature graphic, and light/dark screenshots.