fix: add missing GitBook icons to fiat-moonpay module and changelog

Created by: gatteo

Summary

• Add missing GitBook-compatible icons to fiat-moonpay module pages (configuration, usage, api-reference) to match other modules like wallet-btc
• Add changelog icon for better navigation visibility
• Move changelog to end of overview section in navigation

Changes

• sdk/fiat-modules/fiat-moonpay/configuration.md → icon: gear
• sdk/fiat-modules/fiat-moonpay/usage.md → icon: book-open
• sdk/fiat-modules/fiat-moonpay/api-reference.md → icon: code
• overview/changelog.md → icon: clock-rotate-left
• SUMMARY.md → Reorder changelog position

Test plan

• Verify icons appear correctly in GitBook preview
• Confirm icons match the pattern used in other modules (e.g., wallet-btc)