money: day-by-day forecast with real payment dates

The wealth forecast now runs per day instead of per month, so it shows the
same sawtooth as the actual history:

- recurring items hit on the day the bank history shows (most common day of
  the last four months, clamped to month end), else their start date
- "every N weeks" items (Basic-Fit, haircut) run on an exact N-day cadence
  from the last charge; yearly items on their renewal date
- salary and its extras (holiday pay in May, 13th month in November, bonus,
  settlement) land on the payday from history (contract 25th as fallback),
  moved to the Friday before a weekend; toeslagen move to the Monday after
- variable budgets are spread per day, the vacation budget over Jul-Aug
- excess above the buffer is invested the day after payday; returns
  compound daily
- long horizons stay fast (~35 ms for 100 years): the chart thins each
  pixel bucket to its low and high

src/lib/money-tracker/MoneyChart.svelte

@@ -1,8 +1,15 @@
 <script lang="ts">
-	import { timeGrid, yearLabels, type ChartPoint, type ChartSeries, type GridMode } from './charts';
+	import {
+		decimateSeries,
+		timeGrid,
+		yearLabels,
+		type ChartPoint,
+		type ChartSeries,
+		type GridMode
+	} from './charts';
 
 	let {
-		series,
+		series: input,
 		title,
 		unit = '€',
 		marker,
@@ -24,6 +31,8 @@
 	let compact = $derived(width < 520);
 	let height = $derived(compact ? 240 : 280);
 	let plot = $derived({ left: compact ? 52 : 72, right: 14, top: 18, bottom: 30 });
+	// Daily projections over decades: keep each pixel column's low and high so spikes stay.
+	let series = $derived(decimateSeries(input, width - plot.left - plot.right));
 	let values = $derived(series.flatMap((item) => item.points.map((point) => point.value)));
 	let times = $derived(series.flatMap((item) => item.points.map((point) => time(point.date))));
 	let scale = $derived(niceScale(Math.min(0, ...values), Math.max(0, ...values)));