Merge upstream/main: sync latest updates

- feat(gateway): aggregate all text chunks in non-streaming Gemini responses
- feat(gateway): add SUGGESTION MODE request interception
- feat(oauth): support Anthropic Team accounts with sk authorization
- fix(oauth): update Anthropic OAuth parameters to sync with latest client
- feat: add PromoCodeEnabled setting (default: true)
- resolved conflict: keep TianShuAPI site name while adding PromoCode feature

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

backend/internal/server/api_contract_test.go

@@ -193,20 +193,20 @@ func TestAPIContracts(t *testing.T) {
 				// 普通用户订阅接口不应包含 assigned_* / notes 等管理员字段。
 				deps.userSubRepo.SetByUserID(1, []service.UserSubscription{
 					{
-						ID:           501,
-						UserID:       1,
-						GroupID:      10,
-						StartsAt:     deps.now,
-						ExpiresAt:    deps.now.Add(24 * time.Hour),
-						Status:       service.SubscriptionStatusActive,
+						ID:              501,
+						UserID:          1,
+						GroupID:         10,
+						StartsAt:        deps.now,
+						ExpiresAt:       deps.now.Add(24 * time.Hour),
+						Status:          service.SubscriptionStatusActive,
 						DailyUsageUSD:   1.23,
 						WeeklyUsageUSD:  2.34,
 						MonthlyUsageUSD: 3.45,
-						AssignedBy:    ptr(int64(999)),
-						AssignedAt:    deps.now,
-						Notes:         "admin-note",
-						CreatedAt:     deps.now,
-						UpdatedAt:     deps.now,
+						AssignedBy:      ptr(int64(999)),
+						AssignedAt:      deps.now,
+						Notes:           "admin-note",
+						CreatedAt:       deps.now,
+						UpdatedAt:       deps.now,
 					},
 				})
 			},
@@ -412,6 +412,7 @@ func TestAPIContracts(t *testing.T) {
 				deps.settingRepo.SetAll(map[string]string{
 					service.SettingKeyRegistrationEnabled: "true",
 					service.SettingKeyEmailVerifyEnabled:  "false",
+					service.SettingKeyPromoCodeEnabled:    "true",
 
 					service.SettingKeySMTPHost:     "smtp.example.com",
 					service.SettingKeySMTPPort:     "587",
@@ -450,6 +451,7 @@ func TestAPIContracts(t *testing.T) {
 				"data": {
 					"registration_enabled": true,
 					"email_verify_enabled": false,
+					"promo_code_enabled": true,
 					"smtp_host": "smtp.example.com",
 					"smtp_port": 587,
 					"smtp_username": "user",