🔌 feat(api): extend endpoint type support & expose in pricing UI

* 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.

constant/endpoint_type.go

@@ -8,4 +8,8 @@ const (
 	EndpointTypeAnthropic      EndpointType = "anthropic"
 	EndpointTypeGemini         EndpointType = "gemini"
 	EndpointTypeJinaRerank     EndpointType = "jina-rerank"
+	EndpointTypeMidjourney     EndpointType = "midjourney-proxy"
+	EndpointTypeSuno           EndpointType = "suno-proxy"
+	EndpointTypeKling          EndpointType = "kling"
+	EndpointTypeJimeng         EndpointType = "jimeng"
 )