feat: add MiniMax-M2.5-highspeed to static model list

Add the MiniMax-M2.5-highspeed model variant to the static MiniMax
model list. This model offers the same performance as MiniMax-M2.5
but with faster inference speed.

API docs: https://platform.minimax.io/docs/api-reference/text-openai-api

internal/plugins/ai/openai_compatible/providers_config.go

@@ -195,6 +195,7 @@ func (c *Client) getStaticModels(modelsKey string) ([]string, error) {
 	case "static:minimax":
 		return []string{
 			"MiniMax-M2.5",
+			"MiniMax-M2.5-highspeed",
 			"MiniMax-M2.5-lightning",
 			"MiniMax-M2",
 			"MiniMax-M2.1",