feat: add modular impressum.js, replace martinsiebels.de with msbls.de

- shared/impressum.js: configurable via data-owner and data-style attrs
- Default: minimal msbls.de attribution for satire sites
- Build now copies shared/ to build output
- Caddyfile serves /shared/* globally across all domains
- Removed martinsiebels.de references from 7 KI-satire sites

generate-caddyfile.sh

@@ -14,6 +14,14 @@ cat <<'HEADER'
 :80 {
 HEADER
 
+cat <<'SHARED'
+    # Shared assets available on all domains under /shared/
+    handle /shared/* {
+        root * /srv
+        file_server
+    }
+SHARED
+
 for site_dir in "$SITES_DIR"/*/; do
     [ -f "$site_dir/site.yaml" ] || continue
     domain=$(basename "$site_dir")