fix: make memo input reactive in `SendTransfer`

[goga-m]

Summary

Checklist

• [x] My changes look good in both light AND dark mode
• [x] The change is not hardcoded to a single network, but has multi-asset in mind
• [x] I checked my changes for obvious issues, debug statements and commented code
• [ ] Documentation (if necessary)
• [x] Tests (if necessary)
• [x] Ready to be merged

[faustbrian]

Task linked: CU-mhbz5d [URI] Vendorfield is ignored