feat(ST-360): extend demo seed with claimed and unassigned solo stories

Adds a Solo Demo PBI under the active sprint with 4 stories:
- 3 claimed by demo user, tasks covering TO_DO / IN_PROGRESS / DONE columns
- 1 unassigned story so the sheet demo shows a claimable item

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

prisma/seed.ts

@@ -180,6 +180,92 @@ async function main() {
   }
 
 
+  // Solo board demo data — claimed stories for demo user + 1 unassigned for the sheet
+  const activeSprint = await prisma.sprint.findFirst({
+    where: { product_id: product.id, status: 'ACTIVE' },
+  })
+
+  if (activeSprint) {
+    const soloPbi = await prisma.pbi.create({
+      data: {
+        product_id: product.id,
+        title: 'Solo Demo',
+        description: 'Voorbeeldtaken voor het Solo bord.',
+        priority: 3,
+        sort_order: 99,
+      },
+    })
+
+    const soloData = [
+      {
+        title: 'Gebruikersauthenticatie opzetten',
+        tasks: [
+          { title: 'JWT middleware schrijven', status: 'TO_DO' as const, priority: 1 },
+          { title: 'Login endpoint testen', status: 'TO_DO' as const, priority: 2 },
+        ],
+        assignee_id: demo.id,
+        sortOrder: 1,
+      },
+      {
+        title: 'REST API endpoints implementeren',
+        tasks: [
+          { title: 'Route handlers aanmaken', status: 'IN_PROGRESS' as const, priority: 2 },
+          { title: 'Zod-validatie toevoegen', status: 'TO_DO' as const, priority: 3 },
+        ],
+        assignee_id: demo.id,
+        sortOrder: 2,
+      },
+      {
+        title: 'Database schema migreren',
+        tasks: [
+          { title: 'Prisma schema bijwerken', status: 'DONE' as const, priority: 2 },
+          { title: 'Migratietest uitvoeren', status: 'DONE' as const, priority: 3 },
+        ],
+        assignee_id: demo.id,
+        sortOrder: 3,
+      },
+      {
+        title: 'Frontend unit tests schrijven',
+        tasks: [
+          { title: 'Vitest opzetten', status: 'TO_DO' as const, priority: 3 },
+        ],
+        assignee_id: null,
+        sortOrder: 4,
+      },
+    ]
+
+    for (const s of soloData) {
+      const story = await prisma.story.create({
+        data: {
+          pbi_id: soloPbi.id,
+          product_id: product.id,
+          sprint_id: activeSprint.id,
+          title: s.title,
+          priority: 2,
+          sort_order: 90 + s.sortOrder,
+          status: 'IN_SPRINT',
+          assignee_id: s.assignee_id,
+        },
+      })
+
+      for (let i = 0; i < s.tasks.length; i++) {
+        const t = s.tasks[i]
+        await prisma.task.create({
+          data: {
+            story_id: story.id,
+            sprint_id: activeSprint.id,
+            title: t.title,
+            priority: t.priority,
+            sort_order: i + 1.0,
+            status: t.status,
+          },
+        })
+      }
+    }
+
+    console.log('  Solo demo stories created (3 claimed, 1 unassigned)')
+  }
+
   console.log('\nSeeding complete!')
   console.log('Demo user:  username=demo     password=demo1234')
   console.log('Main user:  username=lars     password=scrum4me123')