fix: correct balance update logic for user and fund in investment and redemption processes

src/app/api/funds/[slug]/invest/route.ts

@@ -70,7 +70,7 @@ export async function POST(req: NextRequest, { params }: { params: { slug: strin
     // Deduct from investor (returns updated user with new balance)
     prisma.user.update({ where: { id: session.user.id }, data: { balance: round2(investor.balance - amount) } }),
     // Add to fund's cash
-    prisma.user.update({ where: { id: fund.userId }, data: { balance: { increment: amount } } }),
+    prisma.user.update({ where: { id: fund.userId }, data: { balance: round2(fund.user.balance + amount) } }),
     // Upsert FundInvestment record
     prisma.fundInvestment.upsert({
       where: { fundId_userId: { fundId: fund.id, userId: session.user.id } },

src/app/api/funds/[slug]/redeem/route.ts

@@ -66,7 +66,7 @@ export async function POST(req: NextRequest, { params }: { params: { slug: strin
     // Return cash to investor
     prisma.user.update({ where: { id: session.user.id }, data: { balance: round2(investor.balance + payout) } }),
     // Deduct from fund's cash
-    prisma.user.update({ where: { id: fund.userId }, data: { balance: { decrement: payout } } }),
+    prisma.user.update({ where: { id: fund.userId }, data: { balance: round2(fund.user.balance - payout) } }),
     // Update or delete FundInvestment
     ...(remainingShares > 0
       ? [prisma.fundInvestment.update({