Component: SprintStatusDonut (Recharts PieChart) (#36)

* chore: voeg recharts toe aan dependencies

Vereist door SprintStatusDonut component.

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

* feat: SprintStatusDonut + getSprintStatusBreakdown helper

PieChart (donut) met TO_DO/IN_PROGRESS/DONE verdeling over alle active sprints.
REVIEW wordt samengevoegd in IN_PROGRESS. MD3 status-kleuren via CSS-variabelen.

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

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/insights/sprint-status.ts

@@ -0,0 +1,39 @@
+import { prisma } from '@/lib/prisma'
+import { productAccessFilter } from '@/lib/product-access'
+
+export type SprintStatusGroup = 'TO_DO' | 'IN_PROGRESS' | 'DONE'
+
+export interface StatusCount {
+  status: SprintStatusGroup
+  count: number
+}
+
+// Maps REVIEW → IN_PROGRESS so donut shows 3 buckets only
+function toGroup(status: string): SprintStatusGroup {
+  if (status === 'DONE') return 'DONE'
+  if (status === 'TO_DO') return 'TO_DO'
+  return 'IN_PROGRESS'
+}
+
+export async function getSprintStatusBreakdown(userId: string): Promise<StatusCount[]> {
+  const tasks = await prisma.task.findMany({
+    where: {
+      story: {
+        sprint: {
+          status: 'ACTIVE',
+          product: productAccessFilter(userId),
+        },
+      },
+    },
+    select: { status: true },
+  })
+
+  const counts: Record<SprintStatusGroup, number> = { TO_DO: 0, IN_PROGRESS: 0, DONE: 0 }
+  for (const t of tasks) {
+    counts[toGroup(t.status)]++
+  }
+
+  return (Object.entries(counts) as [SprintStatusGroup, number][])
+    .filter(([, count]) => count > 0)
+    .map(([status, count]) => ({ status, count }))
+}