feat(ST-902): add setActiveProduct + clearActiveProduct server actions

- actions/active-product.ts: setActiveProductAction validates access via
  productAccessFilter, rejects archived products and demo users
- archiveProductAction: clears active_product_id for all affected users in transaction
- removeProductMemberAction: clears active_product_id for removed member
- leaveProductAction: clears active_product_id for leaving user

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

actions/active-product.ts

@@ -0,0 +1,51 @@
+'use server'
+
+import { revalidatePath } from 'next/cache'
+import { cookies } from 'next/headers'
+import { getIronSession } from 'iron-session'
+import { z } from 'zod'
+import { prisma } from '@/lib/prisma'
+import { SessionData, sessionOptions } from '@/lib/session'
+import { productAccessFilter } from '@/lib/product-access'
+
+async function getSession() {
+  return getIronSession<SessionData>(await cookies(), sessionOptions)
+}
+
+const setSchema = z.object({ productId: z.string().min(1) })
+
+export async function setActiveProductAction(productId: string) {
+  const session = await getSession()
+  if (!session.userId) return { error: 'Niet ingelogd' }
+  if (session.isDemo) return { error: 'Niet beschikbaar in demo-modus' }
+
+  const parsed = setSchema.safeParse({ productId })
+  if (!parsed.success) return { error: 'Ongeldig product-id' }
+
+  const product = await prisma.product.findFirst({
+    where: { id: parsed.data.productId, archived: false, ...productAccessFilter(session.userId) },
+  })
+  if (!product) return { error: 'Product niet gevonden of niet toegankelijk' }
+
+  await prisma.user.update({
+    where: { id: session.userId },
+    data: { active_product_id: parsed.data.productId },
+  })
+
+  revalidatePath('/', 'layout')
+  return { success: true, productId: parsed.data.productId }
+}
+
+export async function clearActiveProductAction() {
+  const session = await getSession()
+  if (!session.userId) return { error: 'Niet ingelogd' }
+  if (session.isDemo) return { error: 'Niet beschikbaar in demo-modus' }
+
+  await prisma.user.update({
+    where: { id: session.userId },
+    data: { active_product_id: null },
+  })
+
+  revalidatePath('/', 'layout')
+  return { success: true }
+}

actions/products.ts

@@ -148,9 +148,16 @@ export async function archiveProductAction(id: string) {
   })
   if (!product) return { error: 'Product niet gevonden' }
 
-  await prisma.product.update({ where: { id }, data: { archived: true } })
+  await prisma.$transaction([
+    // Clear active_product_id for all users who had this product active
+    prisma.user.updateMany({
+      where: { active_product_id: id },
+      data: { active_product_id: null },
+    }),
+    prisma.product.update({ where: { id }, data: { archived: true } }),
+  ])
 
-  revalidatePath('/dashboard')
+  revalidatePath('/', 'layout')
   redirect('/dashboard')
 }
 
@@ -215,7 +222,13 @@ export async function removeProductMemberAction(productId: string, memberId: str
   const product = await prisma.product.findFirst({ where: { id: productId, user_id: session.userId } })
   if (!product) return { error: 'Product niet gevonden of geen eigenaar' }
 
-  await prisma.productMember.deleteMany({ where: { product_id: productId, user_id: memberId } })
+  await prisma.$transaction([
+    prisma.user.updateMany({
+      where: { id: memberId, active_product_id: productId },
+      data: { active_product_id: null },
+    }),
+    prisma.productMember.deleteMany({ where: { product_id: productId, user_id: memberId } }),
+  ])
 
   revalidatePath(`/products/${productId}/settings`)
   return { success: true }
@@ -225,8 +238,15 @@ export async function leaveProductAction(productId: string) {
   const session = await getSession()
   if (!session.userId) return { error: 'Niet ingelogd' }
 
-  await prisma.productMember.deleteMany({ where: { product_id: productId, user_id: session.userId } })
+  await prisma.$transaction([
+    prisma.user.updateMany({
+      where: { id: session.userId, active_product_id: productId },
+      data: { active_product_id: null },
+    }),
+    prisma.productMember.deleteMany({ where: { product_id: productId, user_id: session.userId } }),
+  ])
 
+  revalidatePath('/', 'layout')
   revalidatePath('/settings')
   return { success: true }
 }