Rewrite CI to lint/typecheck/audit/test only; add HPC deployment path

- Replace the Docker build/publish CI stages with ruff (lint + format
  check), ty (type check), pip-audit, and pytest run directly against
  python:3.11-slim; Docker remains for manual/server deployment only.
- Swap black/pylint/mypy for ruff/ty across pyproject.toml, and fix
  every resulting lint, format, and type diagnostic in gallery/ and
  plotstyle/.
- Fix tests broken/stale from before the package restructuring: wrong
  `utils.*` import paths, mock patch targets pointed at the wrong
  module, and PDF-conversion tests still assuming ImageMagick instead
  of the current PyMuPDF-first path. Drop test_container.py (obsolete
  Docker-container smoke tests, fully superseded elsewhere).
- Add a plain-venv + systemd --user timer deployment path
  (deploy/systemd/) for HPC login nodes without a Docker daemon, where
  public_html is already served by existing infrastructure.
- Document both in CLAUDE.md, including running CI's checks locally
  before committing.

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

plotstyle/figures.py

@@ -5,8 +5,8 @@ from __future__ import annotations
 from pathlib import Path
 from typing import Mapping, Sequence, Union
 
-import numpy as np
 import matplotlib.pyplot as plt
+import numpy as np
 from matplotlib.axes import Axes
 from matplotlib.colorbar import Colorbar
 from matplotlib.figure import Figure
@@ -53,8 +53,8 @@ def _set_figure_title(fig: Figure, title: Union[str, None], params: Union[Mappin
 def new_figure(
     preset: Union[str, tuple] = "thesis-single",
     *,
-    title: str = None,
-    params: Mapping = None,
+    title: Union[str, None] = None,
+    params: Union[Mapping, None] = None,
     **subplots_kwargs,
 ):
     """Create a figure/axes pair sized for a named preset or an explicit (w, h) tuple.
@@ -113,7 +113,9 @@ def colorbar(mappable, ax: Axes, size: str = "5%", pad: float = 0.05, **kwargs)
     """
     divider = make_axes_locatable(ax)
     cax = divider.append_axes("right", size=size, pad=pad)
-    cb = ax.get_figure().colorbar(mappable, cax=cax, **kwargs)
+    fig = ax.get_figure()
+    assert fig is not None, "ax must be attached to a figure"
+    cb = fig.colorbar(mappable, cax=cax, **kwargs)
     # Colorbar draws its own border (a dedicated "outline" spine) that isn't
     # covered by axes.spines.{left,right,top} — without this it'd pick up
     # the bold black bottom-spine color/width from the main theme as a box