[FEATURE]:allow editing custom providers from model settings #18224

Feature hasn't been suggested before.

• I have verified this feature I'm about to request hasn't been suggested before.

Describe the enhancement you want to request

Right now custom providers can be added, but they are awkward to update after the initial setup.

If I want to change a custom provider's base URL, headers, display name, or model list, there is no clear edit flow from Settings > Models, even though that page is where the provider's models are managed. In practice this means users may need to disconnect and recreate the provider just to make small changes.

It would be helpful to add an Edit action for custom providers in Settings > Models. Clicking it should open the existing custom provider dialog with the current config prefilled. The provider ID should stay fixed while editing, and saving should update the provider without treating the current ID as a duplicate.

This would make custom OpenAI-compatible providers much easier to maintain, especially for users who frequently update model lists or gateway settings. It would also reduce the chance of losing provider-specific model visibility state when making small config changes.