Changes

PR #1642 by ksylvan: Add --sync-db to generate_changelog, plus many fixes

• Add database synchronization command with comprehensive validation and sync-db flag for database integrity validation
• Implement version and commit existence checking methods with enhanced time parsing using RFC3339Nano fallback support
• Improve timestamp handling and merge commit detection in changelog generator with comprehensive merge commit detection using parents
• Add email field support to PRCommit struct for author information and improve error logging throughout changelog generation
• Optimize merge pattern matching with lazy initialization and thread-safe pattern compilation for better performance

Direct commits

• Chore: incoming 1642 changelog entry

• Fix: improve error message formatting in version date parsing

• Add actual error details to date parsing failure message

• Include error variable in stderr output formatting

• Enhance debugging information for invalid date formats

• Docs: Update CHANGELOG after v1.4.263