ci(docker): rebuild on pyproject.toml changes

app/__init__.py reads __version__ from importlib.metadata, which means
the version baked into the image only refreshes when the build runs
against a checkout where pyproject.toml has the new version. Bumping
the version alone wasn't triggering this workflow, so the :edge image
kept reporting the previous version until an unrelated source change
finally rebuilt it.

Adding pyproject.toml to the watched paths closes that gap.

Author: kallioli

.github/workflows/docker.yml

@@ -11,6 +11,7 @@ on:
       - "static/**"
       - "templates/**"
       - "app/**"
+      - "pyproject.toml"
       - ".github/workflows/docker.yml"
     tags:
       - "v*.*.*"