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

misc/tools.func

@@ -6420,7 +6420,37 @@ function setup_nodejs() {
     msg_ok "Setup Node.js $NODE_VERSION"
   fi
 
-  export NODE_OPTIONS="--max-old-space-size=4096"
+  # Set a safe default heap limit for Node.js builds if not explicitly provided.
+  # Priority:
+  #   1) NODE_OPTIONS (caller/user override)
+  #   2) NODE_MAX_OLD_SPACE_SIZE (explicit MB override)
+  #   3) var_ram (LXC memory setting, MB)
+  #   4) /proc/meminfo (runtime memory detection)
+  # Auto value is clamped to 1024..4096 MB.
+  if [[ -z "${NODE_OPTIONS:-}" ]]; then
+    local node_heap_mb=""
+
+    if [[ -n "${NODE_MAX_OLD_SPACE_SIZE:-}" ]] && [[ "${NODE_MAX_OLD_SPACE_SIZE}" =~ ^[0-9]+$ ]]; then
+      node_heap_mb="${NODE_MAX_OLD_SPACE_SIZE}"
+    elif [[ -n "${var_ram:-}" ]] && [[ "${var_ram}" =~ ^[0-9]+$ ]]; then
+      node_heap_mb=$((var_ram * 75 / 100))
+    else
+      local total_mem_kb=""
+      total_mem_kb=$(awk '/^MemTotal:/ {print $2; exit}' /proc/meminfo 2>/dev/null || echo "")
+      if [[ "$total_mem_kb" =~ ^[0-9]+$ ]]; then
+        local total_mem_mb=$((total_mem_kb / 1024))
+        node_heap_mb=$((total_mem_mb * 75 / 100))
+      fi
+    fi
+
+    if [[ -z "$node_heap_mb" ]] || ((node_heap_mb < 1024)); then
+      node_heap_mb=1024
+    elif ((node_heap_mb > 4096)); then
+      node_heap_mb=4096
+    fi
+
+    export NODE_OPTIONS="--max-old-space-size=${node_heap_mb}"
+  fi
 
   # Ensure valid working directory for npm (avoids uv_cwd error)
   if [[ ! -d /opt ]]; then