Synchronize a fork with upstream

I need the forked repo synced with upstream before the release branch is cut. Update the fork from the original repository arnav-dev/analytics, fast-forward its main and release-2.1 branches, resolve any merge conflicts, then notify Marco and tag the sync as done so he can start QA tomorrow morning.

Before I push a sync to the fork, show me what changed upstream since my last sync: list commits by author and breaking changes, mark files likely to affect our CI, and highlight expected merge conflicts. Produce a short command list I can copy to run the sync and a one-paragraph note for Marco explaining what to re-test.

I fetched arnav-dev/analytics upstream into the fork and now main has conflicts in ci/config.yml and src/db/migrations. I don't know which version our tests expect. Diagnose the likely source of the conflict and give the exact steps to resolve locally (including commands), how to run the unit tests that might reveal regressions, and what to tell Marco about any behavioral risk from the merged changes.

Across multiple projects we branch from stale forks and then hit conflicts late in the sprint. Where am I losing momentum and credibility? Recommend a routine for forks (when and how to sync, CI checks to run before branching, and a short team rule to enforce in PR descriptions) that will cut these issues down by at least half.