Ensure storage directories exist before storage:link in entrypoint

The Docker volume replaces storage/app/ with an empty volume on first
run, so storage/app/public/ must be created explicitly before the
storage:link symlink is registered.

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

docker/entrypoint.sh

@@ -20,8 +20,14 @@ done
 echo "==> Migrationen ausführen..."
 php artisan migrate --force --no-interaction
 
+echo "==> Storage-Verzeichnisse anlegen..."
+mkdir -p storage/app/public \
+         storage/framework/sessions \
+         storage/framework/views \
+         storage/framework/cache/data
+
 echo "==> Storage-Symlink anlegen..."
-php artisan storage:link --force 2>/dev/null || true
+php artisan storage:link --force
 
 echo "==> Cache für Produktion bauen..."
 php artisan config:cache