chore(mods): classify 3 new distribution mods

ars_nouveau, ars_creo and world_dimension_nexus all declare NeoForge
side BOTH and are content mods, so they stay on the server subset.
Create is already in the pack, so ars_creo's dependency is satisfied.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

mods-sides.json

@@ -51,6 +51,8 @@
   "amendments-neoforge-1.21-2.1.5.jar": "both",
   "appleskin-neoforge-mc1.21-3.0.9.jar": "client",
   "architectury-13.0.8-neoforge.jar": "both",
+  "ars_creo-1.21.1-5.4.0.jar": "both",
+  "ars_nouveau-1.21.1-5.12.1.jar": "both",
   "baguettelib-1.21.1-NeoForge-2.0.3.jar": "both",
   "balm-neoforge-1.21.1-21.0.58.jar": "both",
   "buildinggadgets2-1.3.9.jar": "both",
@@ -158,6 +160,7 @@
   "utilitarian-1.21.1-0.19.2.jar": "both",
   "voicechat-neoforge-1.21.1-2.6.18.jar": "both",
   "wm_binaries-3.0.0-rc.1.jar": "client",
+  "world_dimension_nexus-neoforge-1.21.1-0.11.0.jar": "both",
   "yeetusexperimentus-neoforge-87.0.0.jar": "client",
   "yet_another_config_lib_v3-3.8.2+1.21.1-neoforge.jar": "both"
 }