Add facemorph retirement notice

[cdilga]

Summary

• add a fixed bottom retirement notice targeting June 20, 2026 (AEST)
• add feedback links for email and workflow requests
• add a matching FAQ entry explaining the planned service retirement and transition work

Verification

• ran npm run build
• build completed successfully

Notes

• this is intentionally a first user-facing warning, not the full transition page
• the broader Hugging Face migration architecture is being scoped separately

[olivercoad]

Looks like the main problem is that the build job runs on ubuntu-latest which has updated dotnet many many major versions since this project was originally set up.
Dotnet core 3.1 or dotnet 5 is probably the best bet.