chore: Update gitignore to exclude backup directories

- Add .backup/ directory to gitignore
- Add recursive **/.backup/ pattern for nested backup directories

Signed-off-by: Aaron Lippold <[email protected]>

Author: aaronlippold

.gitignore

@@ -14,3 +14,7 @@ session-logs/
 SESSION-RECOVERY.md
 continuation-prompt.md
 CLAUDE.md
+
+# Backup directories
+.backup/
+**/.backup/