Fix brace expansion not working in Alpine sh

Busybox ash does not support brace expansion, so
storage/framework/{sessions,views,cache} was created as a literal
directory name instead of three separate ones. Split into explicit paths.

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

Dockerfile

@@ -37,7 +37,10 @@ COPY . .
 COPY --from=node /app/public/build public/build/
 
 # Autoloader finalisieren
-RUN mkdir -p bootstrap/cache storage/framework/{sessions,views,cache}
+RUN mkdir -p bootstrap/cache \
+    storage/framework/sessions \
+    storage/framework/views \
+    storage/framework/cache
 RUN composer dump-autoload --optimize --no-dev
 
 # Berechtigungen setzen