fix(workflows): Fix empty results in Workflows query type

[idan-starkware]

Fixes #503

• Add nil check for CreatedAt/UpdatedAt timestamps to prevent panics
• Add 'None' option to Time Field dropdown (default) to return all workflows
• Improve time filtering logic with better nil handling
• Add debug logging for troubleshooting

Testing

• ✅ All existing tests pass
• ✅ Tested locally with docker-compose
• ✅ Verified workflows are returned when Time Field is "None"
• ✅ Verified time filtering works with CreatedAt/UpdatedAt options

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