Update README.md

Update README.md

Update welcome screen descriptions with improved messaging

- Change subtitle to 'Your gateway to private, secure, decentralized finance'
- Update 'Untraceable Transactions' to 'Dynamic RingCT for highest privacy'
- Rename 'HEAT Ξmbers Minting' to 'Mint Fuego Ξmbers' with clearer description
- Update 'Private Banking' to 'Private CD Banking' for consistency
- Enhance 'Elderfier Staking' description to mention zkSTARK proofs & cross-chain usage

fix text