Bump container base image to Python 3.12

Dockerfile

@@ -3,9 +3,7 @@ WORKDIR /code
 COPY web-frontend .
 RUN npm install && npm run build
 
-# We cannot upgrade to Python 3.11 until numba supports it.
-# The `sparse` library relies on numba.
-FROM python:3.11-slim as builder
+FROM python:3.12-slim as builder
 
 # We need git at build time in order for versioneer to work, which in turn is
 # needed for the server to correctly report the library_version in the /api/v1/
@@ -40,7 +38,7 @@ RUN TILED_BUILD_SKIP_UI=1 pip install '.[server]'
 # RUN pip install '.[client,dev]'
 # RUN pytest -v
 
-FROM python:3.11-slim as runner
+FROM python:3.12-slim as runner
 
 ENV VIRTUAL_ENV=/opt/venv
 ENV PATH="$VIRTUAL_ENV/bin:$PATH"