Add YAML-based input/output directory configuration to avoid reliance on 8.3 short names on Windows

### Feature Idea

Hello,

I would like to make a feature request regarding how ComfyUI handles custom input and output directories on Windows.

At the moment, input/output paths must be set inside the .bat launcher, like this if the folder is for example in F:\common Comfy\output

- On Windows, if a path contains spaces, Unicode characters, or special symbols, ComfyUI fails to start unless the user manually provides 8.3 short names.
- However, NTFS short names are not guaranteed to exist.
On some Windows installations they are disabled per-drive (disk policy), so users need to:
CMD Windows > enable 8dot3 name creation manually using the command:
fsutil 8dot3name set C: 0
to enable the 8.3 names that ComfyUI cannot otherwise find. (Which explains the vast majority of people struggling to customize their input / output folders path.

This leads to confusing errors where users believe the input/output custom path system “doesn’t work”, because the underlying problem (short names disabled) is not generally known.

Add optional configuration entries in the YAML file (where other custom folder paths already exist), for example:

comfyui:
base_path: E:/path to/models
output_path: E:/whatever path/to/output
input_path: E:/whatever path/to/input
or any naming scheme you prefer.

This would bring several benefits:
- No need for 8.3 short names
Paths could be stored in a normalized, quoted, Unicode-safe format.
- Much cleaner setup
Users wouldn’t need to edit .bat files or rely on legacy filesystem behavior.
- Consistency with existing ComfyUI config system where YAML file already defines custom locations for: checkpoints, loras, embeddings, etc.
- Better portability: Users could move ComfyUI between machines, drives, and OSes without modifying launcher scripts.

Thank you for considering this request.

### Existing Solutions

- activate 8dot3 on a drive if it's not already done:
fsutil 8dot3name set C: 0

- checking the path name in 8dot3 using dir/x in a CMD window.
- add in the .bat files the --input and --output-directory entries, using old 8.3 path names.

### Other

**Why I believe this matters**
On modern Windows, 8.3 short names seem to be disabled for non-system drives. I have 9 drives from C: to K: and for some reason only K: drive had 8.3 disabled. But that's in F: that I decided today to move my input/ouput folders, and how I realized I needed to enable the 8dot3 on F: to make the .bat custom input/ouput entries work.

If paths for input and output are not written in 8.3 format, ComfyUI fails to start or to save ouput/input where we'd want it to.
If paths for input and ouput are written in 8.3 format but 8dot3 is not activated in the drive, ComfyUI will start, but first image created will create a new folder structure in the drive with short 8.3 names visible in windows instead of full names (aka it doesn't find the path).

ComfyUI fails or behaves inconsistently unless the user manually fixes the drive configuration, something most users don't even know how to check (fsutil 8dot3name query d:)

**Allowing these two paths to be configured inside YAML would remove the dependency on legacy DOS naming entirely.**