Data retention hardened; auth callbacks validated

What's Changed

Features

• feat(agent): Move main assistant entrypoint to from side-nav to top-nav (#15160) (44a3fe1d4)

Fixes

• fix: make data retention cleaner more robust against large backlogs (#15195) (06e0e46a0)
• fix(events): resolve comment filters for every event stream (#14976) (86b29b250)
• fix: validate auth callbacks before passing them to nextauth (#15191) (0e32ced9c)
• fix(prompts): isolate linked generation filters (#15193) (8d47da12d)
• fix(trace): keep JSON-viewer meta-root row count in sync after collapse (LANGFUSE-456) (#15174) (98853af1f)

Chores

• chore(agent): Setup CI/CD for building MicroVM images (#15183) (470ca99b7)

Full Changelog: https://github.com/langfuse/langfuse/compare/v3.219.0...v3.220.0