Ship the files pyproject.toml points at

readme and license-files name README.md and LICENSE, but the image only ever
received pyproject.toml, so hatchling failed metadata validation the moment
the layer cache stopped hiding it:

  OSError: Readme file does not exist: README.md

backend/Dockerfile

@@ -1,4 +1,4 @@
-FROM python:3.10
+FROM python:3.13
 
 ENV PYTHONUNBUFFERED=1
 
@@ -35,7 +35,10 @@ RUN --mount=type=cache,target=/root/.cache/uv \
 
 COPY ./backend/scripts /app/backend/scripts
 
-COPY ./backend/pyproject.toml ./backend/alembic.ini /app/backend/
+# README.md and LICENSE come along because pyproject.toml names them in
+# `readme` and `license-files`; hatchling reads both when it builds the
+# package metadata below, and fails the build if either is missing.
+COPY ./backend/pyproject.toml ./backend/alembic.ini ./backend/README.md ./backend/LICENSE /app/backend/
 
 COPY ./backend/fluksio /app/backend/fluksio