phsl / new-api

* backend
  - constant/endpoint_type.go
    • Add EndpointTypeMidjourney, EndpointTypeSuno, EndpointTypeKling, EndpointTypeJimeng.
  - common/endpoint_type.go
    • Map Midjourney / MidjourneyPlus, SunoAPI, Kling, Jimeng channel types to the new endpoint types.

* frontend
  - ModelPricing.js
    • Add “Supported Endpoint Type” column.
    • Implement renderSupportedEndpoints with `stringToColor` for consistent tag colors.

These changes allow `/api/pricing` and model lists to return accurate
`supported_endpoint_types` covering all non-OpenAI providers and display
them clearly in the UI.

No breaking changes.