revert: remove fork-only changes from release sync

Revert payment/wechat, sora/claude-max cleanup, fork-only migrations,
and cosmetic changes that were brought in by the release sync commit.
Keep only channel-monitor related improvements:
- PublicSettingsInjectionPayload named struct with drift test
- ChannelMonitorRunner graceful shutdown in wire
- image_output_price in SupportedModelChip
- Simplified buildSelfNavItems in AppSidebar
- Gateway WARN logs for 503 branches

backend/internal/server/api_contract_test.go

@@ -54,13 +54,8 @@ func TestAPIContracts(t *testing.T) {
 					"username": "alice",
 					"role": "user",
 					"balance": 12.5,
-					"balance_notify_enabled": false,
-					"balance_notify_extra_emails": null,
-					"balance_notify_threshold": null,
-					"balance_notify_threshold_type": "",
 					"concurrency": 5,
 					"status": "active",
-					"total_recharged": 0,
 					"allowed_groups": null,
 					"created_at": "2025-01-02T03:04:05Z",
 					"updated_at": "2025-01-02T03:04:05Z",
@@ -769,13 +764,10 @@ func TestAPIContracts(t *testing.T) {
 					"payment_cancel_rate_limit_unit": "",
 					"payment_cancel_rate_limit_window_mode": "",
 					"balance_low_notify_enabled": false,
+					"account_quota_notify_enabled": false,
 					"balance_low_notify_threshold": 0,
 					"balance_low_notify_recharge_url": "",
-					"account_quota_notify_enabled": false,
 					"account_quota_notify_emails": [],
-					"channel_monitor_enabled": true,
-					"channel_monitor_default_interval_seconds": 60,
-					"available_channels_enabled": false,
 					"wechat_connect_enabled": false,
 					"wechat_connect_app_id": "",
 					"wechat_connect_app_secret_configured": false,
@@ -983,10 +975,7 @@ func TestAPIContracts(t *testing.T) {
 					"auth_source_default_wechat_subscriptions": [],
 					"auth_source_default_wechat_grant_on_signup": false,
 					"auth_source_default_wechat_grant_on_first_bind": false,
-					"force_email_on_third_party_signup": false,
-					"channel_monitor_enabled": true,
-					"channel_monitor_default_interval_seconds": 60,
-					"available_channels_enabled": false
+					"force_email_on_third_party_signup": false
 				}
 			}`,
 		},
@@ -1457,10 +1446,6 @@ func (s *stubAccountRepo) FindByExtraField(ctx context.Context, key string, valu
 	return nil, errors.New("not implemented")
 }
 
-func (s *stubAccountRepo) CountByTLSFingerprintProfile(ctx context.Context) (map[int64]int, error) {
-	return nil, errors.New("not implemented")
-}
-
 func (s *stubAccountRepo) Update(ctx context.Context, account *service.Account) error {
 	return errors.New("not implemented")
 }