[DOCKER] Simplify npm install for devcontainer

[eliteprox]

There are duplicate npm install and unnecessary npm run build commands at different points of the Dockerfile and post-create.sh script, both used by devcontainers

comfystream/docker/Dockerfile

Lines 30 to 32 in eb12b4b

	WORKDIR /workspace/comfystream/ui
	RUN npm install
	RUN npm run build

comfystream/.devcontainer/post-create.sh

Lines 11 to 22 in eb12b4b

	if [ ! -d "/workspace/comfystream/ui/node_modules" ]; then
	echo -e "\e[32mInstalling npm packages for Comfystream UI...\e[0m"
	cd /workspace/comfystream/ui
	npm install
	fi
	if [ ! -d "/workspace/comfystream/nodes/web/static" ]; then
	echo -e "\e[32mBuilding web assets...\e[0m"
	cd /workspace/comfystream/ui
	npm install
	# removed it as we are already getting the built files from install.py
	fi

[linear]

COMFY-161 [DOCKER] Simplify npm install for devcontainer