Cherry-pick: Fix SQLite FK column names don't respect identifier case (#1531)

## Upstream PR
https://github.com/dimitri/pgloader/pull/1531

## Summary
When using `quote identifiers`, foreign key column names from SQLite were not passed through `apply-identifier-case`, causing "column doesn't exist" errors in PostgreSQL.

## Files
- `src/sources/sqlite/sqlite-schema.lisp`

## Notes
- Low risk, 2-line change
- **Priority: Medium**