feat(PBI-63): meerdere sprints per product + EXCLUDED + sprint-switcher

- Sprint lifecycle: ACTIVE→OPEN, COMPLETED→CLOSED, +ARCHIVED (FAILED behouden)
- TaskStatus: +EXCLUDED (overgeslagen door agent-loop via bestaande TO_DO filter)
- Cookie-gebaseerde actieve sprint per product (lib/active-sprint.ts)
- Route splitsen: /products/[id]/sprint/[sprintId] + /sprint redirect-page
- NavBar: gestapelde product/sprint dropdowns + BUILDING-badge derivatie
- Backlog selectie-modus + nieuwe-sprint-dialog (createSprintWithPbisAction)
- Migratie 20260507210000_sprint_lifecycle: ALTER TYPE RENAME (geen data-rewrite)
- Version bump 1.0.0 → 1.2.0

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lib/insights/sprint-status.ts

@@ -20,7 +20,7 @@ export async function getSprintStatusBreakdown(userId: string): Promise<StatusCo
     where: {
       story: {
         sprint: {
-          status: 'ACTIVE',
+          status: 'OPEN',
           product: productAccessFilter(userId),
         },
       },