[Feature Request] Add an option to install custom nodes without automatically installing dependencies

**Is your feature request related to a problem? Please describe.**
Currently, when installing a custom node via ComfyUI Manager, it automatically attempts to install all required dependencies listed in requirements.txt. While this is convenient for beginners, it poses significant risks for advanced users who:
Manage their own Python environment: Users who manually curate their torch, torchaudio, xformers, or other critical library versions to ensure stability across multiple custom nodes.
Fear dependency conflicts: Automatic installation might inadvertently downgrade or upgrade critical packages (like torch), breaking the entire ComfyUI environment.
Prefer manual control: Users who want to inspect the requirements.txt first, verify compatibility, and install dependencies manually via terminal to handle specific flags (e.g., specific CUDA versions) or use mirrors.
Although there are workarounds like setting always_lazy_install = False or using downgrade_blacklist in config.ini, these are global settings that affect all operations and require editing configuration files, which is not user-friendly for a one-off installation.

**Describe alternatives you've considered**
Using pip_blacklist: This prevents specific packages from being installed but doesn't stop the pip install process entirely, and requires knowing the package names beforehand.

**Additional context**
Many users in the community (especially those running large-scale workflows or specific hardware configurations) frequently encounter broken environments due to aggressive auto-dependency resolution. Providing a native UI option to opt-out of this behavior would significantly improve the stability and flexibility of ComfyUI Manager for power users.
Example scenario:
I want to install a new node that requires torch==2.6.0, but my stable environment runs torch==2.8.0. I want to install the node code first, check if it actually works with my current torch version, and only then decide whether to install the specific dependency or find a compatible fork. Currently, the Manager forces the installation immediately.