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>

components/sprint/sprint-run-controls.tsx

@@ -20,7 +20,7 @@ import {
 } from '@/components/ui/dialog'
 import { type PauseContext, pauseReasonLabel } from '@/lib/pause-context'
 
-type SprintStatusValue = 'ACTIVE' | 'COMPLETED' | 'FAILED'
+type SprintStatusValue = 'OPEN' | 'CLOSED' | 'ARCHIVED' | 'FAILED'
 type SprintRunStatusValue =
   | 'QUEUED'
   | 'RUNNING'
@@ -78,7 +78,7 @@ export function SprintRunControls({
       activeSprintRunStatus === 'RUNNING' ||
       activeSprintRunStatus === 'PAUSED')
 
-  const canStart = sprintStatus === 'ACTIVE' && !hasActiveRun
+  const canStart = sprintStatus === 'OPEN' && !hasActiveRun
   const canResume = sprintStatus === 'FAILED'
   const canResumePaused =
     activeSprintRunStatus === 'PAUSED' && pauseContext !== null