feat(sora): 对齐 Sora OAuth 流程并隔离网关请求路径

- 新增并接通 Sora 专用 OAuth 接口与 ST/RT 换取能力
- 完成前端 Sora 授权、RT/ST 手动导入与账号创建流程
- 强化 Sora token 恢复、转发日志与网关路由隔离行为
- 补充后端服务层与路由层相关测试覆盖

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/internal/service/token_refresher_test.go

@@ -226,3 +226,43 @@ func TestClaudeTokenRefresher_CanRefresh(t *testing.T) {
 		})
 	}
 }
+
+func TestOpenAITokenRefresher_CanRefresh(t *testing.T) {
+	refresher := &OpenAITokenRefresher{}
+
+	tests := []struct {
+		name     string
+		platform string
+		accType  string
+		want     bool
+	}{
+		{
+			name:     "openai oauth - can refresh",
+			platform: PlatformOpenAI,
+			accType:  AccountTypeOAuth,
+			want:     true,
+		},
+		{
+			name:     "sora oauth - cannot refresh directly",
+			platform: PlatformSora,
+			accType:  AccountTypeOAuth,
+			want:     false,
+		},
+		{
+			name:     "openai apikey - cannot refresh",
+			platform: PlatformOpenAI,
+			accType:  AccountTypeAPIKey,
+			want:     false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			account := &Account{
+				Platform: tt.platform,
+				Type:     tt.accType,
+			}
+			require.Equal(t, tt.want, refresher.CanRefresh(account))
+		})
+	}
+}