Summary

This changelog update adds the two newly merged upstream fixes to the Unreleased section:

• fix(docker): pin base images to SHA256 digests #7734 by @coygeek: Docker base images are now pinned to SHA256 digests.
• fix: treat HTTP 503 as failover-eligible for LLM provider errors #21086 by @Protocol-zero-0: HTTP 503 provider errors are now treated as failover-eligible.

Greptile Summary

This PR adds two recently merged fixes to the Unreleased section of CHANGELOG.md. The entries follow the established formatting conventions and correctly reference the merged PRs #7734 and #21086 with proper attribution to the respective contributors.

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• The changes are purely documentation updates that add two changelog entries for already-merged PRs. The formatting follows existing conventions, the PR references are accurate, and the authors are correctly attributed. No functional code changes are introduced.
• No files require special attention

_{Last reviewed commit: 4030772}