Move build system from setuptools to uv, wire uv into CI/CD

Convert both pyproject.toml files to the uv_build backend and turn the
repo into a proper uv workspace (plotstyle moved to src layout, since
uv_build requires the module in its own subdirectory). Dev tooling
moves from an optional-dependencies extra to a dependency-group, and
plotstyle's matplotlib dependency is now its own rather than a
gallery "plotting" extra.

Gitea Actions workflows and the Dockerfile now use astral-sh/setup-uv,
uv sync, uv run, uv build, and uv publish throughout instead of pip,
build, and twine. Also fixes .dockerignore, which was excluding
uv.lock, deploy/, and README.md and would have broken even the
previous Dockerfile's COPY of deploy/entrypoint.sh.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

pyproject.toml

@@ -1,6 +1,6 @@
 [build-system]
-requires = ["setuptools>=83.0.0", "wheel"]
-build-backend = "setuptools.build_meta"
+requires = ["uv_build>=0.11.19,<0.12.0"]
+build-backend = "uv_build"
 
 [project]
 name = "gallery"
@@ -43,25 +43,22 @@ dependencies = [
     "textual>=0.50",
 ]
 
-[project.optional-dependencies]
+[project.scripts]
+gallery = "gallery.cli:main"
+
+[dependency-groups]
 dev = [
     "pytest>=7.0",
     "ruff>=0.6",
     "ty>=0.0.1",
     "pip-audit>=2.7",
-    "setuptools>=83.0.0",
-]
-plotting = [
-    "matplotlib>=3.7",
 ]
 
-[project.scripts]
-gallery = "gallery.cli:main"
+[tool.uv.workspace]
+members = ["plotstyle"]
 
-[tool.setuptools]
-packages = ["gallery", "gallery.utils", "gallery.config", "plotstyle"]
-package-data = {gallery = ["templates/*", "assets/css/*", "assets/js/*", "config/*"], plotstyle = ["assets/*.mplstyle"]}
-include-package-data = true
+[tool.uv.build-backend]
+module-root = ""
 
 [tool.ruff]
 line-length = 120