v0.4.0

• Backwards incompatible: the minimum supported Django is now 5.2 LTS.
  Tested against Django 5.2 and 6.0.

• The Polish translation now actually works when installed from PyPI. Django
  reads compiled .mo catalogues rather than the .po sources, and *.mo is
  gitignored, so every release up to and including 0.3.2 shipped the .po
  alone and the translation silently did nothing. Releases now compile the
  catalogues before building, and the build fails if the wheel ends up with
  fewer .mo files than .po files.

• The example/ project, which could not start on any supported Django, is
  replaced by demo/ -- a working project that runs against either the plain
  admin (make demo) or grappelli (make demo-grappelli) from one set of
  models and seed data.

• Documentation is rewritten and published to
  https://mpasternak.github.io/django-flexible-reports/. The previous
  docs/readme.rst included a README.rst that does not exist and
  rendered blank; the install instructions recommended easy_install.

  The manual is now built with MkDocs and the
  Material theme instead of
  Sphinx, and its sources are Markdown.

• Three migrations no longer import
  django.contrib.postgres.fields.jsonb. That import pulled in
  psycopg2 at module load, so migrate failed on SQLite for anyone who
  had installed only the runtime dependencies.

• Table and Report can now be cloned from the admin, using a Clone
  button on the change form. Cloning a table copies its columns and its sort
  order; cloning a report copies its elements, which keep pointing at the same
  tables and datasources. The clone's name gets a translatable (copy)
  suffix.

  Both are also available programmatically as Table.clone() and
  Report.clone(). Neither modifies the source object.

  The button is verified to work with grappelli, which ships its own
  admin/change_form.html; a regression test guards it.

• Fix stale table headers. A cached table class was kept per Table.pk for
  the lifetime of the process and never invalidated, so editing a column's
  label -- or deleting a column -- only became visible after restarting
  Django. With several workers the page alternated between old and new
  headers depending on which worker answered.

  The cache is gone. Compiled column templates are cached instead, keyed by
  the template source so no invalidation is needed, which more than pays the
  removal back: rendering a 500-row table is ~1.25x faster than before, since
  TemplateColumn used to recompile its template for every single cell.