feat: shared backlog filter popover + sprint header polish (v1.3.3) (#184)

- Move sprint switcher into sprint header, centered between title and actions
- Extract BacklogFilterPopover as shared component used by sprint and product backlog
- Add sort options (code/priority/status) with single-pill asc/desc toggle
- Default sprint backlog status filter to OPEN, remove "alleen niet klaar" button
- Persist collapsed state and filter popover open in localStorage
- Fix hydration flicker: defer localStorage read to useEffect with prefsLoaded gate for writes
- Increase sprint switcher text size for readability

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

app/(app)/products/[id]/sprint/[sprintId]/page.tsx

@@ -11,7 +11,6 @@ import {
 import { SprintTaskDialogMount } from '@/components/sprint/sprint-task-dialog-mount'
 import { SprintUrlTaskSync } from '@/components/sprint/sprint-url-task-sync'
 import { SyncActiveSprintCookie } from '@/components/sprint/sync-active-sprint-cookie'
-import { SprintSwitcher } from '@/components/shared/sprint-switcher'
 import { getSprintSwitcherData } from '@/lib/sprint-switcher-data'
 import { SprintHeader } from '@/components/sprint/sprint-header'
 import { SprintRunControls } from '@/components/sprint/sprint-run-controls'
@@ -182,22 +181,17 @@ export default async function SprintBoardPage({ params, searchParams }: Props) {
   }
 
   return (
-    <div className="flex flex-col h-full">
+    <div id="wrapper2" className="flex flex-col h-full">
       <SyncActiveSprintCookie productId={id} sprintId={sprint.id} />
-      <div className="px-4 py-3 border-b border-border bg-surface-container-low shrink-0 flex items-center justify-center">
-        <SprintSwitcher
-          productId={id}
-          sprints={switcherData.sprintItems}
-          activeSprint={switcherData.activeSprintItem}
-          buildingSprintIds={switcherData.buildingSprintIds}
-        />
-      </div>
       <SprintHeader
         productId={id}
         productName={product.name}
         sprint={sprint}
         isDemo={isDemo}
         sprintStories={sprintStoryItems}
+        switcherSprints={switcherData.sprintItems}
+        switcherActiveSprint={switcherData.activeSprintItem}
+        switcherBuildingSprintIds={switcherData.buildingSprintIds}
       />
 
       <div className="border-b border-border bg-surface-container-low px-4 py-2 shrink-0">