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>

plotstyle/pyproject.toml

@@ -0,0 +1,37 @@
+[build-system]
+requires = ["uv_build>=0.11.19,<0.12.0"]
+build-backend = "uv_build"
+
+[project]
+name = "plotstyle"
+version = "0.1.0"
+description = "KIT corporate-design matplotlib styling toolkit for consistent scientific figures"
+readme = "README.md"
+requires-python = ">=3.8"
+license = {text = "MIT"}
+authors = [
+    {name = "K. Schmidt"},
+]
+keywords = [
+    "matplotlib",
+    "plotting",
+    "scientific-computing",
+    "styling",
+]
+classifiers = [
+    "Development Status :: 3 - Alpha",
+    "Intended Audience :: Science/Research",
+    "License :: OSI Approved :: MIT License",
+    "Operating System :: OS Independent",
+    "Programming Language :: Python :: 3",
+    "Programming Language :: Python :: 3.8",
+    "Programming Language :: Python :: 3.9",
+    "Programming Language :: Python :: 3.10",
+    "Programming Language :: Python :: 3.11",
+    "Programming Language :: Python :: 3.12",
+    "Topic :: Scientific/Engineering :: Visualization",
+]
+
+dependencies = [
+    "matplotlib>=3.7",
+]