Add +-1000 spinner buttons to amount fields, floor (not round) to nearest 1000 in all allocation calculations

src/app/api/phases/[phaseId]/transition/route.ts

@@ -2,6 +2,7 @@ import { NextRequest, NextResponse } from "next/server";
 import { z } from "zod";
 import { prisma } from "@/lib/db";
 import { computeSecurityYearlyValues } from "@/lib/calculations";
+import { floorToThousand } from "@/lib/format";
 
 const transitionItemSchema = z.object({
   positionType: z.enum(["SECURITY", "REAL_ESTATE"]),
@@ -132,6 +133,11 @@ export async function PUT(
     }
   }
 
+  // Auf ein Vielfaches von 1'000 abrunden, damit der Betrag ueber Wertschriften
+  // (die nur in 1'000er-Schritten Sparbeitraege/Startwerte annehmen) vollstaendig
+  // verteilbar bleibt.
+  incomingCapital = floorToThousand(incomingCapital);
+
   const transition = await prisma.$transaction(async (tx) => {
     await tx.phaseTransition.deleteMany({ where: { fromPhaseId: phaseId } });