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  Docker-container smoke tests, fully superseded elsewhere).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/annotations.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import warnings
+from typing import Optional
 
 from matplotlib.axes import Axes
 from matplotlib.colors import to_rgba
@@ -21,7 +22,7 @@ def style_legend(
     ax: Axes,
     loc: str = "outside right upper",
     frameon: bool = False,
-    title: str = None,
+    title: Optional[str] = None,
     **kwargs,
 ):
     """Add a figure-level legend, placed outside the axes by default.
@@ -43,12 +44,15 @@ def style_legend(
         )
 
     fig = ax.get_figure()
+    assert fig is not None, "ax must be attached to a figure"
     handles = kwargs.pop("handles", None)
     labels = kwargs.pop("labels", None)
     if handles is None or labels is None:
         handles, labels = ax.get_legend_handles_labels()
 
-    legend = fig.legend(handles, labels, loc=loc, frameon=frameon, title=title, **kwargs)
+    # matplotlib-stubs' `loc` Literal doesn't include the "outside ..." compound
+    # locations matplotlib actually supports at runtime (e.g. "outside right upper").
+    legend = fig.legend(handles, labels, loc=loc, frameon=frameon, title=title, **kwargs)  # ty: ignore[invalid-argument-type]
     if legend.get_title() is not None:
         legend.get_title().set_fontweight("bold")
     return legend