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/task-status.ts

@@ -15,6 +15,7 @@ const TASK_DB_TO_API = {
   REVIEW: 'review',
   DONE: 'done',
   FAILED: 'failed',
+  EXCLUDED: 'excluded',
 } as const satisfies Record<TaskStatus, string>
 
 const TASK_API_TO_DB: Record<string, TaskStatus> = {
@@ -23,6 +24,7 @@ const TASK_API_TO_DB: Record<string, TaskStatus> = {
   review: 'REVIEW',
   done: 'DONE',
   failed: 'FAILED',
+  excluded: 'EXCLUDED',
 }
 
 const STORY_DB_TO_API = {
@@ -54,14 +56,16 @@ const PBI_API_TO_DB: Record<string, PbiStatus> = {
 }
 
 const SPRINT_DB_TO_API = {
-  ACTIVE: 'active',
-  COMPLETED: 'completed',
+  OPEN: 'open',
+  CLOSED: 'closed',
+  ARCHIVED: 'archived',
   FAILED: 'failed',
 } as const satisfies Record<SprintStatus, string>
 
 const SPRINT_API_TO_DB: Record<string, SprintStatus> = {
-  active: 'ACTIVE',
-  completed: 'COMPLETED',
+  open: 'OPEN',
+  closed: 'CLOSED',
+  archived: 'ARCHIVED',
   failed: 'FAILED',
 }