feat: statusbalk met versie en builddatum

Voegt sticky statusbalk toe aan de onderkant van de app met:
- Copyright melding
- App-versie uit package.json (NEXT_PUBLIC_APP_VERSION)
- Builddatum ingesteld op het moment van de build (NEXT_PUBLIC_BUILD_DATE)

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

components/shared/status-bar.tsx

@@ -0,0 +1,18 @@
+const buildDate = process.env.NEXT_PUBLIC_BUILD_DATE
+  ? new Date(process.env.NEXT_PUBLIC_BUILD_DATE).toLocaleDateString('nl-NL', {
+      day: 'numeric',
+      month: 'short',
+      year: 'numeric',
+    })
+  : '—'
+
+const version = process.env.NEXT_PUBLIC_APP_VERSION ?? '0.0.0'
+
+export function StatusBar() {
+  return (
+    <footer className="shrink-0 border-t border-border bg-surface-container-low px-4 py-1 flex items-center justify-between text-[10px] text-muted-foreground select-none">
+      <span>© {new Date().getFullYear()} Scrum4Me</span>
+      <span>v{version} · gebouwd op {buildDate}</span>
+    </footer>
+  )
+}