chore: gitignore local .beads-ats.env (untracked env file with a home path)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: renezander030

.gitignore

@@ -28,3 +28,4 @@ scripts/.pii-denylist
 *.db
 .beads-credential-key
 .beads/proxieddb/
+.beads-ats.env