Create CHANGELOG.md (litmus-otas)
Add a CHANGELOG.md to track releases. Start with v0.3.0 (screenshot system + R2 deployment) and backfill v0.2.0 and v0.1.0 from git history.
Summary of Changes
Created CHANGELOG.md with entries for v0.1.0, v0.2.0, v0.3.0, and Unreleased. Backfilled from git history across main and dev branches.