feat(nodejs): auto-size NODE_OPTIONS heap and apply in Termix updates

- setup_nodejs now sets NODE_OPTIONS only when not already set
- Heap size is auto-derived from NODE_MAX_OLD_SPACE_SIZE, var_ram, or MemTotal
- Auto heap is clamped to 1024..4096 MB to avoid too-small or too-large defaults
- Termix update path now calls setup_nodejs before frontend/backend builds so
  Node heap defaults are applied consistently during updates

ct/termix.sh

@@ -155,6 +155,8 @@ EOF
       /opt/termix/nginx/client_body
     msg_ok "Recreated Directories"
 
+    NODE_VERSION="24" setup_nodejs
+
     msg_info "Building Frontend"
     cd /opt/termix
     export COREPACK_ENABLE_DOWNLOAD_PROMPT=0