feat(settings): channel_monitor_show_quota public setting (default off)

- 新增公开设置 key（迁移 226 已插入默认 false），控制用户端监控页
  是否展示配额/余额；管理端不受影响
- 解析 fail-closed：仅字面 "true" 视为开启（对齐 available_channels_enabled
  语义，而非 hide_throughput 的 fail-open）
- 全链路贯通：domain key 常量 → setting_public（公开读取 + ChannelMonitorRuntime
  .ShowQuota + 注入 payload）→ settings_view/parse/update → handler DTO
  （admin/user 响应 + admin 更新请求）→ api_contract_test 两个 wantJSON 块

backend/internal/handler/admin/setting_handler.go

@@ -374,6 +374,7 @@ func (h *SettingHandler) GetSettings(c *gin.Context) {
 		ChannelMonitorMode:                   settings.ChannelMonitorMode,
 		ChannelMonitorDefaultIntervalSeconds: settings.ChannelMonitorDefaultIntervalSeconds,
 		ChannelMonitorHideThroughput:         settings.ChannelMonitorHideThroughput,
+		ChannelMonitorShowQuota:              settings.ChannelMonitorShowQuota,
 
 		GrokDefaultTextModel:           settings.GrokDefaultTextModel,
 		GrokCrossClientModelMapEnabled: settings.GrokCrossClientModelMapEnabled,

backend/internal/handler/admin/setting_handler_update.go

@@ -332,6 +332,7 @@ type UpdateSettingsRequest struct {
 	ChannelMonitorMode                   *string `json:"channel_monitor_mode"`
 	ChannelMonitorDefaultIntervalSeconds *int    `json:"channel_monitor_default_interval_seconds"`
 	ChannelMonitorHideThroughput         *bool   `json:"channel_monitor_hide_throughput"`
+	ChannelMonitorShowQuota              *bool   `json:"channel_monitor_show_quota"`
 
 	// Grok model mapping policy
 	GrokDefaultTextModel           *string `json:"grok_default_text_model"`
@@ -1889,6 +1890,12 @@ func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 			}
 			return previousSettings.ChannelMonitorHideThroughput
 		}(),
+		ChannelMonitorShowQuota: func() bool {
+			if req.ChannelMonitorShowQuota != nil {
+				return *req.ChannelMonitorShowQuota
+			}
+			return previousSettings.ChannelMonitorShowQuota
+		}(),
 		GrokDefaultTextModel: func() string {
 			if req.GrokDefaultTextModel != nil {
 				return *req.GrokDefaultTextModel
@@ -2342,6 +2349,7 @@ func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 		ChannelMonitorMode:                   updatedSettings.ChannelMonitorMode,
 		ChannelMonitorDefaultIntervalSeconds: updatedSettings.ChannelMonitorDefaultIntervalSeconds,
 		ChannelMonitorHideThroughput:         updatedSettings.ChannelMonitorHideThroughput,
+		ChannelMonitorShowQuota:              updatedSettings.ChannelMonitorShowQuota,
 
 		GrokDefaultTextModel:           updatedSettings.GrokDefaultTextModel,
 		GrokCrossClientModelMapEnabled: updatedSettings.GrokCrossClientModelMapEnabled,

backend/internal/handler/dto/settings.go

@@ -305,6 +305,7 @@ type SystemSettings struct {
 	ChannelMonitorMode                   string `json:"channel_monitor_mode"`
 	ChannelMonitorDefaultIntervalSeconds int    `json:"channel_monitor_default_interval_seconds"`
 	ChannelMonitorHideThroughput         bool   `json:"channel_monitor_hide_throughput"`
+	ChannelMonitorShowQuota              bool   `json:"channel_monitor_show_quota"`
 
 	// Grok model mapping policy (admin settings; empty account mapping falls back to these).
 	GrokDefaultTextModel           string `json:"grok_default_text_model"`
@@ -414,6 +415,7 @@ type PublicSettings struct {
 	ChannelMonitorMode                   string `json:"channel_monitor_mode"`
 	ChannelMonitorDefaultIntervalSeconds int    `json:"channel_monitor_default_interval_seconds"`
 	ChannelMonitorHideThroughput         bool   `json:"channel_monitor_hide_throughput"`
+	ChannelMonitorShowQuota              bool   `json:"channel_monitor_show_quota"`
 
 	AvailableChannelsEnabled bool `json:"available_channels_enabled"`
 

backend/internal/handler/setting_handler.go

@@ -107,6 +107,7 @@ func (h *SettingHandler) GetPublicSettings(c *gin.Context) {
 		ChannelMonitorMode:                   settings.ChannelMonitorMode,
 		ChannelMonitorDefaultIntervalSeconds: settings.ChannelMonitorDefaultIntervalSeconds,
 		ChannelMonitorHideThroughput:         settings.ChannelMonitorHideThroughput,
+		ChannelMonitorShowQuota:              settings.ChannelMonitorShowQuota,
 
 		AvailableChannelsEnabled: settings.AvailableChannelsEnabled,
 

backend/internal/server/api_contract_test.go

@@ -988,6 +988,7 @@ func TestAPIContracts(t *testing.T) {
 					"channel_monitor_enabled": true,
 					"channel_monitor_mode": "v1",
 					"channel_monitor_hide_throughput": true,
+					"channel_monitor_show_quota": false,
 					"channel_monitor_default_interval_seconds": 60,
 					"available_channels_enabled": false,
 					"model_plaza_enabled": false,
@@ -1298,6 +1299,7 @@ func TestAPIContracts(t *testing.T) {
 					"channel_monitor_enabled": true,
 					"channel_monitor_mode": "v1",
 					"channel_monitor_hide_throughput": true,
+					"channel_monitor_show_quota": false,
 					"channel_monitor_default_interval_seconds": 60,
 					"available_channels_enabled": false,
 					"model_plaza_enabled": false,

backend/internal/service/domain_constants.go

@@ -477,6 +477,13 @@ const (
 	// Default false (show rates). Admin endpoints always keep full metrics.
 	SettingKeyChannelMonitorHideThroughput = "channel_monitor_hide_throughput"
 
+	// SettingKeyChannelMonitorShowQuota controls whether quota/balance snapshots
+	// attached to channel monitors (check_mode=quota/quota_probe) are exposed on
+	// the user-facing monitor APIs and UI. Default false (hidden); parsed
+	// fail-closed (only the literal "true" enables it). Admin endpoints always
+	// keep the full snapshots regardless of this flag.
+	SettingKeyChannelMonitorShowQuota = "channel_monitor_show_quota"
+
 	// SettingKeyGrokDefaultTextModel is the fallback Grok text model for empty
 	// request models and built-in Grok aliases (e.g. "grok" → this id). Default grok-4.5.
 	SettingKeyGrokDefaultTextModel = "grok_default_text_model"

backend/internal/service/setting_parse.go

@@ -190,6 +190,7 @@ func (s *SettingService) InitializeDefaultSettings(ctx context.Context) error {
 		SettingKeyChannelMonitorMode:                   ChannelMonitorModeV1,
 		SettingKeyChannelMonitorDefaultIntervalSeconds: "60",
 		SettingKeyChannelMonitorHideThroughput:         "true",
+		SettingKeyChannelMonitorShowQuota:              "false",
 
 		// Grok: safe defaults — no cross-vendor model rewrite unless operators enable it.
 		SettingKeyGrokDefaultTextModel:           "grok-4.5",
@@ -798,6 +799,9 @@ func (s *SettingService) parseSettings(settings map[string]string) *SystemSettin
 	// 默认隐藏吞吐（迁移 206 的隐私默认）：未配置时必须与 setting_public.go 的
 	// 公开读取路径给出同一个值，否则管理端看到“未隐藏”而用户端实际已隐藏。
 	result.ChannelMonitorHideThroughput = !isFalseSettingValue(settings[SettingKeyChannelMonitorHideThroughput])
+	// 配额展示默认关闭且 fail-closed：仅字面 "true" 视为开启
+	// （与 setting_public.go 公开读取路径保持一致）。
+	result.ChannelMonitorShowQuota = settings[SettingKeyChannelMonitorShowQuota] == "true"
 
 	// Grok default mapping policy
 	result.GrokDefaultTextModel = strings.TrimSpace(settings[SettingKeyGrokDefaultTextModel])

backend/internal/service/setting_public.go

@@ -231,6 +231,7 @@ func (s *SettingService) GetPublicSettings(ctx context.Context) (*PublicSettings
 		SettingKeyChannelMonitorMode,
 		SettingKeyChannelMonitorDefaultIntervalSeconds,
 		SettingKeyChannelMonitorHideThroughput,
+		SettingKeyChannelMonitorShowQuota,
 		SettingKeyAvailableChannelsEnabled,
 		SettingKeyModelPlazaEnabled,
 		SettingKeyModelPlazaRequireAuth,
@@ -355,6 +356,7 @@ func (s *SettingService) GetPublicSettings(ctx context.Context) (*PublicSettings
 		ChannelMonitorMode:                   normalizeChannelMonitorMode(settings[SettingKeyChannelMonitorMode]),
 		ChannelMonitorDefaultIntervalSeconds: parseChannelMonitorInterval(settings[SettingKeyChannelMonitorDefaultIntervalSeconds]),
 		ChannelMonitorHideThroughput:         !isFalseSettingValue(settings[SettingKeyChannelMonitorHideThroughput]),
+		ChannelMonitorShowQuota:              settings[SettingKeyChannelMonitorShowQuota] == "true",
 
 		AvailableChannelsEnabled: settings[SettingKeyAvailableChannelsEnabled] == "true",
 
@@ -422,6 +424,10 @@ type ChannelMonitorRuntime struct {
 	DefaultIntervalSeconds int
 	// HideThroughput: when true, user-facing V2 APIs omit RPM/TPM scale signals.
 	HideThroughput bool
+	// ShowQuota: when true, user-facing monitor views keep the quota/balance
+	// snapshots; otherwise the user handler strips them server-side.
+	// Parsed fail-closed (only literal "true" enables). Admin always sees them.
+	ShowQuota bool
 }
 
 // ActiveProbesAllowed reports whether V1 active provider probes may run.
@@ -450,6 +456,7 @@ func (s *SettingService) GetChannelMonitorRuntime(ctx context.Context) ChannelMo
 		SettingKeyChannelMonitorMode,
 		SettingKeyChannelMonitorDefaultIntervalSeconds,
 		SettingKeyChannelMonitorHideThroughput,
+		SettingKeyChannelMonitorShowQuota,
 	})
 	if err != nil {
 		return ChannelMonitorRuntime{
@@ -464,6 +471,7 @@ func (s *SettingService) GetChannelMonitorRuntime(ctx context.Context) ChannelMo
 		Mode:                   normalizeChannelMonitorMode(vals[SettingKeyChannelMonitorMode]),
 		DefaultIntervalSeconds: parseChannelMonitorInterval(vals[SettingKeyChannelMonitorDefaultIntervalSeconds]),
 		HideThroughput:         !isFalseSettingValue(vals[SettingKeyChannelMonitorHideThroughput]),
+		ShowQuota:              vals[SettingKeyChannelMonitorShowQuota] == "true",
 	}
 }
 
@@ -606,6 +614,9 @@ type PublicSettingsInjectionPayload struct {
 	// ChannelMonitorHideThroughput is public so the user UI can hide RPM/TPM
 	// without waiting for API redaction alone (defense in depth).
 	ChannelMonitorHideThroughput bool `json:"channel_monitor_hide_throughput"`
+	// ChannelMonitorShowQuota gates the user-facing quota/balance display on
+	// monitors; fail-closed (absent/false = hidden). Admin UI always shows it.
+	ChannelMonitorShowQuota bool `json:"channel_monitor_show_quota"`
 	AvailableChannelsEnabled     bool `json:"available_channels_enabled"`
 	ModelPlazaEnabled            bool `json:"model_plaza_enabled"`
 	ModelPlazaRequireAuth        bool `json:"model_plaza_require_auth"`
@@ -685,6 +696,7 @@ func (s *SettingService) GetPublicSettingsForInjection(ctx context.Context) (any
 		ChannelMonitorMode:                   settings.ChannelMonitorMode,
 		ChannelMonitorDefaultIntervalSeconds: settings.ChannelMonitorDefaultIntervalSeconds,
 		ChannelMonitorHideThroughput:         settings.ChannelMonitorHideThroughput,
+		ChannelMonitorShowQuota:              settings.ChannelMonitorShowQuota,
 		AvailableChannelsEnabled:             settings.AvailableChannelsEnabled,
 		ModelPlazaEnabled:                    settings.ModelPlazaEnabled,
 		ModelPlazaRequireAuth:                settings.ModelPlazaRequireAuth,

backend/internal/service/setting_update.go

@@ -417,6 +417,7 @@ func (s *SettingService) buildSystemSettingsUpdates(ctx context.Context, setting
 		updates[SettingKeyChannelMonitorDefaultIntervalSeconds] = strconv.Itoa(v)
 	}
 	updates[SettingKeyChannelMonitorHideThroughput] = strconv.FormatBool(settings.ChannelMonitorHideThroughput)
+	updates[SettingKeyChannelMonitorShowQuota] = strconv.FormatBool(settings.ChannelMonitorShowQuota)
 
 	// Grok model mapping policy
 	if v := strings.TrimSpace(settings.GrokDefaultTextModel); v != "" {

backend/internal/service/settings_view.go

@@ -201,6 +201,7 @@ type SystemSettings struct {
 	ChannelMonitorMode                   string `json:"channel_monitor_mode"`
 	ChannelMonitorDefaultIntervalSeconds int    `json:"channel_monitor_default_interval_seconds"`
 	ChannelMonitorHideThroughput         bool   `json:"channel_monitor_hide_throughput"`
+	ChannelMonitorShowQuota              bool   `json:"channel_monitor_show_quota"`
 
 	// Grok model mapping policy (admin settings; empty mapping falls back to these).
 	GrokDefaultTextModel           string `json:"grok_default_text_model"`
@@ -378,6 +379,7 @@ type PublicSettings struct {
 	ChannelMonitorMode                   string `json:"channel_monitor_mode"`
 	ChannelMonitorDefaultIntervalSeconds int    `json:"channel_monitor_default_interval_seconds"`
 	ChannelMonitorHideThroughput         bool   `json:"channel_monitor_hide_throughput"`
+	ChannelMonitorShowQuota              bool   `json:"channel_monitor_show_quota"`
 
 	// Grok model mapping policy (admin settings).
 	GrokDefaultTextModel           string `json:"grok_default_text_model"`