feat(migration-bundle): add collection-level selection and file filtering

[fefehun]

Summary

This PR adds collection-level selection functionality to the migration-bundle extension, allowing users to select specific collections to migrate instead of migrating all content at once.

Addresses: #266, #294

Features Added

• Collection-Level Selection: Users can now select specific collections for schema and content migration
• File Filtering: Only files referenced by selected collections are migrated
• Parent Group Auto-Inclusion: When child collections are selected, parent group collections are automatically included
• Schema Option: Added "Schema" as a selectable migration option (previously always migrated)
• Filtered System Data: Panels, flows, presets, and comments are now filtered based on collection references
• Environment Variables:
  • MIGRATION_BUNDLE_SELECTED_COLLECTIONS
  • MIGRATION_BUNDLE_EXCLUDED_COLLECTIONS

Important Note: PostgreSQL Requirement

Due to a known Directus bug (#20428), schema migrations may fail on MySQL target instances. The bug causes char(36) to varchar(36) conversion which breaks MySQL foreign key constraints.

Recommendation: Use PostgreSQL for the target instance.

Target Database	Schema Migration	Status
PostgreSQL	✅ Works correctly	Recommended
MySQL	⚠️ May fail with FK errors	Known issue

Test Plan

• Test migration with specific collections selected (schema + content)
• Verify parent group collections are auto-included
• Test file filtering with selected collections
• Verify panels/flows/presets are filtered by collection
• Test with PostgreSQL target instance

Development Note: This feature was developed with assistance from Claude Code (Anthropic's AI coding assistant).

🤖 Generated with Claude Code