Make copyright year configurable via 'year' YAML variable, default 2026

Change-Id: Ibdf26a92b252198f57384636c31d065f07e1564f
diff --git a/inst/rmarkdown/templates/posterdown_ids/resources/template.html b/inst/rmarkdown/templates/posterdown_ids/resources/template.html
index 2babb84..88cb7f0 100644
--- a/inst/rmarkdown/templates/posterdown_ids/resources/template.html
+++ b/inst/rmarkdown/templates/posterdown_ids/resources/template.html
@@ -754,7 +754,7 @@
 info@ids-mannheim.de<br/>
 www.ids-mannheim.de<br/>
 <br/>
-© 2025 IDS Mannheim/$if(lang.de)$ÖA$else$PR$endif$<br/>
+© $if(year)$$year$$else$2026$endif$ IDS Mannheim/$if(lang.de)$ÖA$else$PR$endif$<br/>
 <br/>
 $if(lang.de)$
 <svg