Add blanko build target, fix preamble duplication, update event config and margins

- Add --blanko flag to generate_cards.py for blank cards (no CSV needed), 2-up layout
- Fix preamble duplication bug affecting both blanko and multi-participant personalized builds
- Add make build-blanko target; default make now builds personalized + blanko
- Reduce page margins from 0.8cm to 0.4cm for Kyocera P6026
- Widen tikzpicture columns (6.9→7.2cm) and tabular columns (6.6→7.0cm) to fill page width
- Update event.yml for BRM400 Bonn–Lüttich–Bastogne–Bonn, 9. Mai 2026, with 6 controls

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

Makefile

@@ -2,15 +2,17 @@
 
 IMAGE_NAME := brevetcard-builder
 TEX_FILE_PERSONALIZED := brevetkarte-personalized.tex
+TEX_FILE_BLANKO := brevetkarte-blanko.tex
 TEX_FILE_BACK := brevetkarte-rueckseite.tex
 PDF_FILE_PERSONALIZED := brevetkarte-personalized.pdf
+PDF_FILE_BLANKO := brevetkarte-blanko.pdf
 PDF_FILE_BACK := brevetkarte-rueckseite.pdf
 CSV_FILE := export_brevetcard.csv
 
-.PHONY: all build clean build-image build-back generate build-personalized run shell help
+.PHONY: all build clean build-image build-back generate build-personalized build-blanko run shell help
 
 # Default target
-all: build-personalized
+all: build-personalized build-blanko
 
 # Build Docker image
 build-image:
@@ -50,6 +52,23 @@ build-personalized: generate build-image
 		pdflatex -interaction=nonstopmode $(TEX_FILE_BACK)
 	@echo "PDF generated: $(PDF_FILE_BACK)"
 
+# Build blank (blanko) front + event back side PDFs (no CSV required)
+build-blanko: build-image
+	@echo "Generating blank card..."
+	python3 generate_cards.py --blanko
+	@echo "Compiling blank front side to PDF..."
+	docker run --rm \
+		-v $(PWD):/workspace \
+		$(IMAGE_NAME) \
+		pdflatex -interaction=nonstopmode $(TEX_FILE_BLANKO)
+	@echo "PDF generated: $(PDF_FILE_BLANKO)"
+	@echo "Compiling back side to PDF..."
+	docker run --rm \
+		-v $(PWD):/workspace \
+		$(IMAGE_NAME) \
+		pdflatex -interaction=nonstopmode $(TEX_FILE_BACK)
+	@echo "PDF generated: $(PDF_FILE_BACK)"
+
 # Run container interactively
 run:
 	docker run --rm -it \
@@ -86,6 +105,7 @@ help:
 	@echo "  make build-image        - Build Docker image only"
 	@echo "  make generate           - Generate tex files from CSV + event.yml"
 	@echo "  make build-personalized - Generate and compile front + back side PDFs"
+	@echo "  make build-blanko       - Generate and compile blank card (no CSV needed)"
 	@echo "  make build-back         - Compile back side PDF only (after generate)"
 	@echo "  make shell              - Open interactive shell in container"
 	@echo "  make clean              - Remove generated files (aux, log, pdf)"