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  Docker-container smoke tests, fully superseded elsewhere).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>

gallery/utils/stats.py

@@ -30,9 +30,9 @@ def calculate_directory_stats(directory: Path) -> dict:
             size = item.stat().st_size
             stats["total_size"] += size
 
-            if item.suffix.lower() == '.pdf':
+            if item.suffix.lower() == ".pdf":
                 stats["pdf_size"] += size
-            elif item.suffix.lower() == '.png':
+            elif item.suffix.lower() == ".png":
                 stats["png_size"] += size
         elif item.is_dir():
             stats["folder_count"] += 1