feat(fassets): update auto-redeem guides for shared FAssetRedeemComposer

Update auto-redemption docs and examples to use the shared pre-deployed
FAssetRedeemComposer contract (0x80c5eb...) on Coston2.

- Update compose encoding to match RedeemComposeData struct (address, string)
- Add COMPOSE_VALUE for executor fee forwarding
- Replace per-user composer deployment with shared contract references
- Update FAssetRedeemComposer.sol to match deployed implementation
- Convert ASCII flow diagrams to Mermaid sequence diagrams

Author: 0xreflexivity