[enhancement]: Allow user to set default model

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Contact Details

Discord: shanedk

### What should this feature add?

When the user resets the Web UI, the model that is selected seems to be whichever happens to be first alphabetically. It would be convenient in such times for the user to be able to go to a model in the Model Manager and select a "Set as default" option, so that the model, model settings, and resolution would be set to the defaults for that model. That way, the user wouldn't have to go through all the options setting them up again.

### Alternatives

_No response_

### Additional Content

Example: A user has `a-zovya-photoreal` installed, and when resetting the UI this model is selected, with a resolution of 512x512, Euler, 50 steps, and CFG 7.5.

The user has `JuggernautXL` installed, and has set it for 30 steps with CFG 3 and DPM++ 2S Karras. With this enhancement, the user would set `JuggernautXL` as the default, and when the UI is reset, it would be automatically selected with his preferred scheduler, steps, and CFG, with the model's default resolution of 1024x1024 (unless the user has specified something different in the model settings).

Then, upon resetting the UI, the user can quickly enter prompts, check other settings, and get going again.