Support multiple example files per template

[Empreiteiro]

Summary

• Allow uploading multiple example documents when creating a template
• When multiple files are provided, AI processes all of them and compares differences to build a unified field set
• Fields present in all documents are marked as required, fields in only some are marked optional
• Template detail page shows list of example files with ability to add/remove individual files
• New API endpoints: POST /api/templates/{id}/example-files and DELETE /api/templates/{id}/example-files/{index}
• DB migration renames example_file (single path) to example_files (JSON array) with backward-compatible data conversion

Test plan

• Create a template with a single file — verify field suggestion works as before
• Create a template with 2+ different example documents — verify AI analyzes all and suggests unified fields
• On template detail page, add more example files via drag-and-drop
• Remove individual example files from the list
• Click "Re-suggest Fields" with multiple files — verify multi-doc analysis runs
• Verify existing templates with legacy single-file data still work after migration

🤖 Generated with Claude Code