SQL: Date Spine via Recursive CTE

> This problem is paper-only - see explanation for the canonical SQL solution. Build a "date spine" - one row per day - between two ISO dates inclusive, useful for filling gaps in time-series reports. In Postgres you'd use `generate_series`; in MySQL / SQL Server you'd use a recursive CTE. **For the auto-grader:** implement `dateSpine(start, end)` returning `["YYYY-MM-DD"]` ascending. Cap output at 1000 rows.