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  Docker-container smoke tests, fully superseded elsewhere).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

@@ -21,17 +21,23 @@ Example usage:
 __version__ = "0.1.0"
 __author__ = "K. Schmidt"
 
+from gallery.api import generate
+from gallery.builder import build_gallery, get_template
 from gallery.config import (
     GalleryConfig,
-    GallerySource,
     GalleryDefaults,
+    GallerySource,
 )
-from gallery.api import generate
-
-# Export utility functions for testing and advanced usage
-from gallery.utils.stats import (
-    calculate_directory_stats,
-    format_file_size,
+from gallery.utils.datetime_utils import (
+    datetime_from_timestamp,
+    strftime_filter,
+)
+from gallery.utils.metadata import (
+    load_folder_metadata,
+    load_metadata_file,
+    merge_metadata,
+    resolve_metadata_for_plot,
+    save_metadata_cache,
 )
 from gallery.utils.processing import (
     convert_pdf_to_png,
@@ -39,18 +45,12 @@ from gallery.utils.processing import (
     process_plot_files,
     render_gallery_page,
 )
-from gallery.utils.metadata import (
-    load_folder_metadata,
-    merge_metadata,
-    save_metadata_cache,
-    load_metadata_file,
-    resolve_metadata_for_plot,
+
+# Export utility functions for testing and advanced usage
+from gallery.utils.stats import (
+    calculate_directory_stats,
+    format_file_size,
 )
-from gallery.utils.datetime_utils import (
-    datetime_from_timestamp,
-    strftime_filter,
-)
-from gallery.builder import build_gallery, get_template
 
 __all__ = [
     "generate",
@@ -74,4 +74,3 @@ __all__ = [
     "datetime_from_timestamp",
     "strftime_filter",
 ]
-