feat: add media seed controls and dimension swap

[Minamiyama]

Summary

Add consistent seed controls to image, video, and audio generation WebUIs, and add a width/height swap button wherever both dimensions are configurable.

Changes

• Add Seed(s) support for image generation.
  • Accept comma-separated seeds.
  • Default to -1.
  • Pad missing seeds to the requested image count on the backend.
  • Treat missing values and -1 as random seeds.
  • Regenerate exactly one fresh seed per requested image whenever 🎲 is clicked.
• Add scalar seed controls to video and audio generation.
• Pass seeds through the existing kwargs API field.
• Normalize and forward seeds across supported image, video, and audio backends.
• Safely ignore seeds when the underlying model does not support them.
• Add width/height swap controls to image and video forms.
• Add frontend and backend seed utility tests.

API Examples

Image generation:

{
  "n": 4,
  "kwargs": "{\"seed\":[11,22]}"
}

This is handled as [11, 22, -1, -1].

Video and audio generation:

{
  "kwargs": "{\"seed\":11}"
}

Compatibility

No top-level API schema changes. Seed values continue to use the existing kwargs passthrough mechanism.

[gemini-code-assist]

Warning

You have reached your daily quota limit. Please wait up to 24 hours and I will start processing your requests again!