sync: bring over remaining release/custom-0.1.115 changes

- Extract PublicSettingsInjectionPayload named struct with drift test
- Add channel_monitor_default_interval_seconds to SSR injection
- Add image_output_price to SupportedModelChip
- Simplify AppSidebar buildSelfNavItems (admins see available channels)
- Add gateway WARN logs for 503 no-available-accounts branches
- Wire ChannelMonitorRunner into provideCleanup for graceful shutdown
- Add migrations 130/131 (CC template userid fix + mimicry field cleanup)
- Clean up fork-only features (sora, claude max simulation, client affinity)
- Remove ~320 obsolete i18n keys
- Add codexUsage utility, WechatServiceButton, BulkEditAccountModal
- Tidy go.sum

backend/internal/service/error_policy_test.go

@@ -110,13 +110,12 @@ func TestCheckErrorPolicy(t *testing.T) {
 			expected:   ErrorPolicyTempUnscheduled,
 		},
 		{
-			// Antigravity 401 不走升级逻辑（由 applyErrorPolicy 的 temp_unschedulable_rules 自行控制），
-			// second hit 仍然返回 TempUnscheduled。
-			name: "temp_unschedulable_401_second_hit_antigravity_stays_temp",
+			// Gemini OAuth 401 second hit 会升级为 error（返回 None，交由默认错误逻辑处理）。
+			name: "temp_unschedulable_401_second_hit_gemini_escalates",
 			account: &Account{
 				ID:                      15,
 				Type:                    AccountTypeOAuth,
-				Platform:                PlatformAntigravity,
+				Platform:                PlatformGemini, // 非 Antigravity 平台 401 second hit 升级
 				TempUnschedulableReason: `{"status_code":401,"until_unix":1735689600}`,
 				Credentials: map[string]any{
 					"temp_unschedulable_enabled": true,
@@ -131,7 +130,29 @@ func TestCheckErrorPolicy(t *testing.T) {
 			},
 			statusCode: 401,
 			body:       []byte(`unauthorized`),
-			expected:   ErrorPolicyTempUnscheduled,
+			expected:   ErrorPolicyNone, // Gemini 401 second hit 升级为 error
+		},
+		{
+			name: "temp_unschedulable_401_antigravity_no_escalation",
+			account: &Account{
+				ID:                      16,
+				Type:                    AccountTypeOAuth,
+				Platform:                PlatformAntigravity, // Antigravity 跳过 401 升级，由 rules 正常处理
+				TempUnschedulableReason: `{"status_code":401,"until_unix":1735689600}`,
+				Credentials: map[string]any{
+					"temp_unschedulable_enabled": true,
+					"temp_unschedulable_rules": []any{
+						map[string]any{
+							"error_code":       float64(401),
+							"keywords":         []any{"unauthorized"},
+							"duration_minutes": float64(10),
+						},
+					},
+				},
+			},
+			statusCode: 401,
+			body:       []byte(`unauthorized`),
+			expected:   ErrorPolicyTempUnscheduled, // Antigravity 不升级，继续走规则匹配
 		},
 		{
 			name: "temp_unschedulable_body_miss_returns_none",