Add VideoDeltaNet-H3 Model

### Model/Pipeline/Scheduler description

VideoDeltaNet (VDN-H3) is a hybrid-attention variant of MiniMax H3 designed for faster video generation with near-lossless quality. It replaces dense video-video attention with a combination of local sliding-window softmax attention and long-range linear attention, while keeping the original H3 backbone largely unchanged.

All weights and training and inference code are available.

### Open source status

- [x] The model implementation is available.
- [x] The model weights are available (Only relevant if addition is not a scheduler).

### Provide useful links for the implementation

Weight: https://huggingface.co/OpenVDN/vdn-minimax-h3
Code: https://github.com/OpenVDN/vdn-minimax-h3
I'm the author :)

Start by reading the model implementation at https://github.com/OpenVDN/vdn-minimax-h3 and reviewing the weights at https://huggingface.co/OpenVDN/vdn-minimax-h3. Then compare the implementation with existing diffusers model, pipeline, and scheduler integrations. Done means VideoDeltaNet-H3 is added to diffusers with its available weights and documented inference support.

Written by the indexing model from the issue text.