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

Caddyfile

@@ -4,6 +4,11 @@
 }
 
 :80 {
+    # Shared assets available on all domains under /shared/
+    handle /shared/* {
+        root * /srv
+        file_server
+    }
     @allaisonme_com host allaisonme.com
     handle @allaisonme_com {
         root * /srv/allaisonme.com