Design and implement database migration framework for schema evolution

[cfuehrmann]

Problem

As nutriterm approaches v1.0 and beyond, we need a comprehensive migration framework to handle schema changes without breaking user data. Users must be able to safely upgrade nutriterm versions regardless of how their data format needs to evolve.

Dependencies

• Blocked by: Issue Add schema versioning infrastructure to support future migration strategies #4 (Schema versioning infrastructure)
  • Requires version detection and workspace metadata
  • Migration framework depends on version comparison capabilities
  • Cannot implement migrations without knowing current/target schema versions

Proposed Solution

Design and implement a complete migration framework that provides:

Migration System

• Safe data transformation when schemas evolve
• Support for various migration types (additive, transformative, breaking)
• Backup and rollback capabilities
• Progress reporting for large workspaces

User Experience

• Clear migration commands (nutriterm migrate, --dry-run, etc.)
• Automatic migration detection and prompting
• Comprehensive error handling and recovery
• Migration history tracking

Migration Strategy Flexibility

• Support for automatic migrations (safe changes)
• Interactive migrations (requiring user decisions)
• Manual migration guidance for complex cases
• Batch processing for multiple workspaces

Key Design Questions

• Migration trigger mechanism (automatic detection vs explicit commands)
• Handling of complex transformations requiring user input
• Backward compatibility timeline and support strategy
• Recovery mechanisms for failed migrations
• Support for version skipping (e.g., v1 → v3 direct migration)

Goals

• Users never lose data due to schema changes
• Schema evolution doesn't disrupt existing workflows
• Excellent user experience during version upgrades
• Sustainable development process for future schema changes
• Professional-grade reliability and safety

Success Criteria

• Migration framework handles all anticipated schema evolution patterns
• Users can confidently upgrade nutriterm versions
• Data integrity maintained throughout all migration processes
• Clear documentation and migration guidance
• Comprehensive test coverage for migration scenarios
• Framework ready before v1.0 release

This migration framework is critical infrastructure that enables nutriterm to evolve safely post-v1.0 while protecting user data.