Switch to debian:bookworm-slim, drop enumitem and texlive-latex-extra

- Replace texlive/texlive:latest with debian:bookworm-slim + targeted
  TeX Live packages (texlive-latex-recommended, texlive-pictures,
  texlive-fonts-recommended)
- Remove \usepackage{enumitem} from brevetkarte.tex and template;
  replace list options with plain LaTeX \setlength equivalents
- Add Export Brevetkarte.csv to .gitignore (real participant data)
- Add Export Brevetkarte.csv.example with anonymised sample data

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitignore

@@ -9,6 +9,10 @@
 
 # Rendered PDFs
 *.pdf
+*.bak
+
+# Real participant data (copy to "Export Brevetkarte.csv" and fill in)
+Export Brevetkarte.csv
 
 # Generated files
 brevetkarte-personalized.tex