Spend anomaly watch

Compare the period since this task last ran against the same length of
time before it. Read only. Change nothing.

Source: WHERE.
Threshold: flag a change above PERCENT percent or CURRENCY AMOUNT,
whichever is smaller.

State the two periods and both totals before anything else. Every
figure below sits inside those two windows.

Then four groups.

Larger. Line items above the threshold. Show the earlier figure, the
later figure, the difference and the percentage, with the subtraction
visible. Largest difference first.
Smaller. The same, for drops. A drop matters as much as a rise and is
noticed far less.
New. Line items present in the later period and absent in the earlier
one.
Stopped. Present earlier, absent later.

Then a line for what you could not compare: renamed line items,
currency changes, or a category that only exists on one side. Never
let one of those appear as New or Stopped without saying so.

Rules. Do not explain why anything changed. Do not call anything waste.
Currency is stated once, and mixed currencies are kept separate rather
than converted.