feat: 补充gpt生图模型测试功能

Author: Wei-Shaw

backend/internal/pkg/openai/constants.go

@@ -20,6 +20,8 @@ var DefaultModels = []Model{
 	{ID: "gpt-5.3-codex", Object: "model", Created: 1735689600, OwnedBy: "openai", Type: "model", DisplayName: "GPT-5.3 Codex"},
 	{ID: "gpt-5.3-codex-spark", Object: "model", Created: 1735689600, OwnedBy: "openai", Type: "model", DisplayName: "GPT-5.3 Codex Spark"},
 	{ID: "gpt-5.2", Object: "model", Created: 1733875200, OwnedBy: "openai", Type: "model", DisplayName: "GPT-5.2"},
+	{ID: "gpt-image-1", Object: "model", Created: 1733875200, OwnedBy: "openai", Type: "model", DisplayName: "GPT Image 1"},
+	{ID: "gpt-image-1.5", Object: "model", Created: 1735689600, OwnedBy: "openai", Type: "model", DisplayName: "GPT Image 1.5"},
 	{ID: "gpt-image-2", Object: "model", Created: 1738368000, OwnedBy: "openai", Type: "model", DisplayName: "GPT Image 2"},
 }