fix: update permissions for store_creds volume in Dockerfile

Dockerfile

@@ -19,8 +19,10 @@ RUN uv sync --frozen --no-dev
 RUN useradd --create-home --shell /bin/bash app \
     && chown -R app:app /app
 
-# Give read access to the store_creds volume
-RUN chmod -R 755 /app/store_creds
+# Give read and write access to the store_creds volume
+RUN mkdir -p /app/store_creds \
+    && chown -R app:app /app/store_creds \
+    && chmod 755 /app/store_creds
 
 USER app