Feature request: "Average per month" option for the Cash Flow (Sankey) chart

[kisst]

Problem

The Cash Flow (Sankey) chart shows totals for the selected period (30D, 90D, 365D, …). For a household budget view, yearly or quarterly bills (internet, insurance, taxes, car service) either show up as spikes in short periods or need mental division in long ones. The question I actually want answered is: what does a typical month cost us, and where does a typical month's income go?

Proposal

Add an "Average per month" option to the Cash Flow widget, e.g. a toggle, or period choices like "Avg / month: 3M · 6M · 12M":

• Compute the same Sankey over the last N complete calendar months (the current, partially filled month would skew the average).
• Divide every node and link value by N. Percentages stay the same; only the absolute values change.
• Show income, spending and surplus per month next to the chart.

This makes recurring but infrequent costs visible at their real monthly weight (e.g. a ~1'000/year internet bill shows as ~85/month instead of a spike in one month), and makes the chart directly usable for "cost of living per month" discussions in a household.

Notes

I'm running this locally as a small add-on that reuses the dashboard's existing Sankey builder with a custom period of the last N full months and divides the values by N, so it fits the current data model without new queries. It has been very useful for us, so I wanted to share the idea.