[Feature Request]: Allow for selection of video used for color coherence.

### Is there an existing issue for this?

- [X] I have searched the existing issues and checked the recent builds/commits

### What would your feature do ?

Currently, the `Color Coherence` open of `Video Input` uses the video defined in `Init -> Video Init`, but it would be beneficial to have an additional field called `Alt Video Init` that allows the user to define which video to use. In this way, the user had a lot more control over the color coherence.

### Proposed workflow

Adding a video file name field under `Color Coherence` when `Alt Video Input` is selected

### Additional information

This could be implemented by extracting the frames from a video to subfolder called "colorframes" if `Alt Video Init` is activated, and then in `render.py` there would be added similar code to what exists now:

```
if anim_args.color_coherence == 'Alt Video Input' and hybrid_available:
if int(frame_idx) % int(anim_args.color_coherence_video_every_N_frames) == 0:
prev_vid_img = Image.open(os.path.join(args.outdir, 'colorframes', get_frame_name(anim_args.video_init_path) + f"{frame_idx:09}.jpg"))
prev_vid_img = prev_vid_img.resize((args.W, args.H), PIL.Image.LANCZOS)
color_match_sample = np.asarray(prev_vid_img)
color_match_sample = cv2.cvtColor(color_match_sample, cv2.COLOR_RGB2BGR)
```
The number of frames generated in `colorframes` would be equal to the number of frames in `inputframes`, but the user could a video of any length, and the extracting code could easily calculate the correct number of frames via interpolation. expansion, and decimation.

### Are you going to help adding it?

I am happy to contribute to the degree I am capable of. I have looked at the code, and I have more questions than understanding about it, but this task seems simple enough for me to attempt if I get a few pointers.

My discord ID is 1064991849149898822

Trace the Color Coherence and Video Init settings, then inspect render.py and the existing inputframes extraction path. Implement the Alt Video Init selection and colorframes generation so Color Coherence reads the selected video, with frame counts aligned to inputframes and interpolation or decimation handled as described.

Written by the indexing model from the issue text.