71. Daily Cumulative Sales (RANGE vs ROWS)

When an OVER clause has ORDER BY keys with ties, the frame mode matters:

• RANGE frames group all peer rows (rows equal on the ORDER BY key) together — they all share one running value.
• ROWS frames count physical rows one at a time, so tied rows get different running values depending on physical order.

The daily_sales table has multiple sale rows per sale_date. We want a per-day cumulative total: every row of a given day should show the same running total, namely the sum of all sales on that day and all earlier days. That requires a RANGE frame.

Task: return each sale with its correct per-day cumulative total.

Return columns sale_date, amount, cume_total, ordered by sale_date ascending, then amount ascending.