Add stack Update, ComfyUI model manager, and slim ComfyUI stack.

Server UI gains Update on stack cards, ComfyUI Models tab with workflow
scan and downloads, and centralized comfyui_config. Model catalog and
download scripts move from stacks/comfyui to server-ui so ComfyUI stays a
minimal Docker wrapper for easier image updates.

stacks/comfyui/scripts/ensure-dirs.sh

@@ -5,13 +5,25 @@ ensure_comfyui_dirs() {
   local data_root="${1:-/data}"
   mkdir -p \
     "${data_root}/apps/comfyui/storage" \
-    "${data_root}/apps/comfyui/models" \
+    "${data_root}/apps/comfyui/models/checkpoints" \
+    "${data_root}/apps/comfyui/models/loras" \
+    "${data_root}/apps/comfyui/models/vae" \
+    "${data_root}/apps/comfyui/models/controlnet" \
+    "${data_root}/apps/comfyui/models/upscale_models" \
+    "${data_root}/apps/comfyui/models/clip" \
+    "${data_root}/apps/comfyui/models/unet" \
     "${data_root}/apps/comfyui/cache/hf-hub" \
     "${data_root}/apps/comfyui/cache/torch-hub" \
     "${data_root}/apps/comfyui/input" \
     "${data_root}/apps/comfyui/output" \
     "${data_root}/apps/comfyui/custom_nodes" \
     "${data_root}/apps/comfyui/workflows"
+
+  # Host downloads (Server UI / CLI) need write access; container (root) can still write.
+  local owner="${COMFYUI_DATA_OWNER:-${SUDO_USER:-}}"
+  if [[ "${EUID}" -eq 0 && -n "${owner}" ]]; then
+    chown -R "${owner}:${owner}" "${data_root}/apps/comfyui/models"
+  fi
 }
 
 if [[ "${BASH_SOURCE[0]}" == "${0}" ]]; then