Per-user campaign storage and public campaign list

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

nginx.conf

@@ -34,7 +34,7 @@ server {
         resolver 127.0.0.11 valid=10s ipv6=off;
         set $saves http://saves:8080;
         proxy_pass $saves;
-        client_max_body_size 2m;
+        client_max_body_size 33m; # campaigns up to 32 MB (server/src/main.rs MAX_CAMPAIGN)
         proxy_read_timeout 15s;
     }
 }