feat: ST-101-ST-110 M1 producten, PBI backlog, iconen en PWA manifest

- Product aanmaken/bewerken/archiveren/herstellen (ST-101, ST-103)
- SplitPane component met versleepbare splitter en localStorage (ST-104)
- PanelNavBar herbruikbaar paneelheader component (ST-105)
- PbiList met prioriteitsgroepen, inline aanmaken, filter en verwijderen (ST-106-ST-110)
- StoryPanel placeholder rechter paneel met selectie via Zustand (ST-109)
- App iconen geinstalleerd: favicon, apple-icon, PWA manifest (192/512px)
- AppIcon SVG component in navigatiebar
- Root layout metadata bijgewerkt naar Nederlands

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

components/backlog/story-panel.tsx

@@ -0,0 +1,56 @@
+'use client'
+
+import { useSelectionStore } from '@/stores/selection-store'
+import { PanelNavBar } from '@/components/shared/panel-nav-bar'
+
+interface Story {
+  id: string
+  title: string
+  status: string
+}
+
+interface StoryPanelProps {
+  storiesByPbi: Record<string, Story[]>
+  isDemo: boolean
+}
+
+export function StoryPanel({ storiesByPbi, isDemo }: StoryPanelProps) {
+  const { selectedPbiId } = useSelectionStore()
+
+  const stories = selectedPbiId ? (storiesByPbi[selectedPbiId] ?? []) : null
+
+  return (
+    <div className="flex flex-col h-full">
+      <PanelNavBar
+        title="Stories"
+        actions={
+          selectedPbiId && !isDemo ? (
+            <button className="text-xs text-primary hover:underline">+ Story</button>
+          ) : undefined
+        }
+      />
+      <div className="flex-1 overflow-y-auto p-4">
+        {stories === null ? (
+          <p className="text-sm text-muted-foreground text-center mt-8">
+            Selecteer een PBI om de stories te bekijken.
+          </p>
+        ) : stories.length === 0 ? (
+          <p className="text-sm text-muted-foreground text-center mt-8">
+            Nog geen stories voor dit PBI.
+          </p>
+        ) : (
+          <div className="space-y-2">
+            {stories.map(story => (
+              <div
+                key={story.id}
+                className="bg-surface-container-low border border-border rounded-lg p-3 text-sm"
+              >
+                {story.title}
+              </div>
+            ))}
+          </div>
+        )}
+      </div>
+    </div>
+  )
+}