Update to Python 3.12

Just update various dependencies.

Dockerfile

-FROM python:3.11-slim AS compile-image
+FROM python:3.12-slim AS compile-image
 RUN apt-get update
 RUN apt-get install -y --no-install-recommends git
 # We're only using the root user, pip shouldn't warn about it
@@ -16,7 +16,7 @@ COPY .git/ .git/
 COPY geosphere_api/ geosphere_api/
 RUN pip install --user . -r requirements.txt
 
-FROM python:3.11-slim AS build-image
+FROM python:3.12-slim AS build-image
 COPY --from=compile-image /root/.local /root/.local
 
 # Make sure scripts in .local are usable: