build: create /app/static. there is more static media to collect

Dockerfile

@@ -40,11 +40,7 @@ RUN adduser --home /app --no-create-home --system --uid ${AURA_UID} --group app
     # containers. We therefore create them here and set the permissions right away
     # since named volumes otherwise create these directories themself as the root
     # user.
-    mkdir -p \
-    /app/site_media \
-    /app/static/admin \
-    /app/logs \
-    && \
+    mkdir -p /app/site_media /app/static /app/logs && \
     chown -R app:app /app
 
 USER app