fix python version conflict in docker builds

Author: jnptk

backend/Dockerfile

@@ -1,5 +1,5 @@
 # syntax=docker/dockerfile:1.9
-ARG PYTHON_VERSION=3.12
+ARG PYTHON_VERSION=3.14
 FROM plone/server-builder:uv-${PYTHON_VERSION} AS builder
 
 # Install dependencies
@@ -54,4 +54,4 @@ COPY --from=builder --chown=500:500 /app /app
 RUN <<EOT
     ln -s /data /app/var
     chown -R 500:500 /data
-EOT
+EOT