Money tracker: Knab CSV import, multi-bank linking, sum reconcile, history range

- Knab statement exports: per-account ids (knab:<account>:<Referentie>), routed by IBAN,
  transfers between own accounts merged into one tracker account are dropped (interest kept)
- Import: multiple files, hand-entered twins get the import id, hand entries equal to the
  sum of 2-3 payments within a day are replaced by them
- bank-link --bank revolut|abn|knab with per-bank default account; ASPSP notes printed
- bank-sync: longest history on an account first sync (--full to force), sum reconcile,
  per-session status so one bank failing does not mark the others
- Timeline: 1 year / 3 years / All history range

src/lib/money-tracker/charts.ts

@@ -306,3 +306,28 @@ export function utilityEstimate(
 		differenceCents: advancesCents - estimatedCents
 	};
 }
+
+export type HistoryRange = '1y' | '3y' | 'all';
+
+/** First date shown for a history range (null = everything). */
+export function historyStart(range: HistoryRange, today: string): string | null {
+	if (range === 'all') return null;
+	const years = range === '1y' ? 1 : 3;
+	return `${Number(today.slice(0, 4)) - years}${today.slice(4)}`;
+}
+
+/**
+ * Hides history before `from`, starting each line at `from` with the balance it had then,
+ * so a long bank history doesn't squash the recent months.
+ */
+export function clipSeries(series: ChartSeries[], from: string | null): ChartSeries[] {
+	if (!from) return series;
+	return series.map((line) => {
+		const before = line.points.filter((point) => point.date < from);
+		const after = line.points.filter((point) => point.date >= from);
+		const carried = before.at(-1);
+		const points =
+			carried && after[0]?.date !== from ? [{ date: from, value: carried.value }, ...after] : after;
+		return { ...line, points };
+	});
+}