feat(PBI-63): meerdere sprints per product + EXCLUDED + sprint-switcher (#161)

- 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/tasks-status-update.ts

@@ -131,15 +131,15 @@ export async function propagateStatusUpwards(
 
       let nextStatus: SprintStatus
       if (anyPbiFailed) nextStatus = 'FAILED'
-      else if (allPbisDone) nextStatus = 'COMPLETED'
-      else nextStatus = 'ACTIVE'
+      else if (allPbisDone) nextStatus = 'CLOSED'
+      else nextStatus = 'OPEN'
 
       if (nextStatus !== sprint.status) {
         await tx.sprint.update({
           where: { id: sprint.id },
           data: {
             status: nextStatus,
-            ...(nextStatus === 'COMPLETED' ? { completed_at: new Date() } : {}),
+            ...(nextStatus === 'CLOSED' ? { completed_at: new Date() } : {}),
           },
         })
         sprintChanged = true
@@ -149,7 +149,7 @@ export async function propagateStatusUpwards(
 
     // SprintRun herevalueren — via ClaudeJob.sprint_run_id van deze task
     let sprintRunChanged = false
-    if (nextSprintStatus === 'FAILED' || nextSprintStatus === 'COMPLETED') {
+    if (nextSprintStatus === 'FAILED' || nextSprintStatus === 'CLOSED') {
       const job = await tx.claudeJob.findFirst({
         where: { task_id: taskId, sprint_run_id: { not: null } },
         orderBy: { created_at: 'desc' },