feat(websearch): settings UI overhaul and quota improvements

- Remove Priority field, auto load-balance by quota remaining
- Replace QuotaRefreshInterval (daily/weekly/monthly) with SubscribedAt
  (subscription date, monthly lazy refresh via Redis TTL)
- Add collapsible provider cards, API key show/copy, usage progress bar
- Add test endpoint (POST /web-search-emulation/test) bypassing quota
- Wire WebSearchManagerBuilder on startup (was never called before)
- Fix nextMonthlyReset day-of-month overflow (Jan 31 → Feb 28)
- Fix non-deterministic sort in selectByQuotaWeight
- Map ProxyID in builder for provider-level proxy tracking
- Fix frontend timezone drift in subscribed_at date picker
- Fix provider deletion index shift for expandedProviders state

backend/internal/handler/admin/setting_handler.go

@@ -175,9 +175,7 @@ func (h *SettingHandler) GetSettings(c *gin.Context) {
 		EnableFingerprintUnification:         settings.EnableFingerprintUnification,
 		EnableMetadataPassthrough:            settings.EnableMetadataPassthrough,
 		EnableCCHSigning:                     settings.EnableCCHSigning,
-		BalanceLowNotifyEnabled:              settings.BalanceLowNotifyEnabled,
-		BalanceLowNotifyThreshold:            settings.BalanceLowNotifyThreshold,
-		AccountQuotaNotifyEmails:             settings.AccountQuotaNotifyEmails,
+		WebSearchEmulationEnabled:            settings.WebSearchEmulationEnabled,
 		PaymentEnabled:                       paymentCfg.Enabled,
 		PaymentMinAmount:                     paymentCfg.MinAmount,
 		PaymentMaxAmount:                     paymentCfg.MaxAmount,
@@ -307,11 +305,6 @@ type UpdateSettingsRequest struct {
 	EnableMetadataPassthrough    *bool `json:"enable_metadata_passthrough"`
 	EnableCCHSigning             *bool `json:"enable_cch_signing"`
 
-	// Balance low notification
-	BalanceLowNotifyEnabled   *bool     `json:"balance_low_notify_enabled"`
-	BalanceLowNotifyThreshold *float64  `json:"balance_low_notify_threshold"`
-	AccountQuotaNotifyEmails  *[]string `json:"account_quota_notify_emails"`
-
 	// Payment configuration (integrated into settings, full replace)
 	PaymentEnabled           *bool    `json:"payment_enabled"`
 	PaymentMinAmount         *float64 `json:"payment_min_amount"`
@@ -889,24 +882,6 @@ func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 			}
 			return previousSettings.EnableCCHSigning
 		}(),
-		BalanceLowNotifyEnabled: func() bool {
-			if req.BalanceLowNotifyEnabled != nil {
-				return *req.BalanceLowNotifyEnabled
-			}
-			return previousSettings.BalanceLowNotifyEnabled
-		}(),
-		BalanceLowNotifyThreshold: func() float64 {
-			if req.BalanceLowNotifyThreshold != nil {
-				return *req.BalanceLowNotifyThreshold
-			}
-			return previousSettings.BalanceLowNotifyThreshold
-		}(),
-		AccountQuotaNotifyEmails: func() []string {
-			if req.AccountQuotaNotifyEmails != nil {
-				return *req.AccountQuotaNotifyEmails
-			}
-			return previousSettings.AccountQuotaNotifyEmails
-		}(),
 	}
 
 	if err := h.settingService.UpdateSettings(c.Request.Context(), settings); err != nil {
@@ -1053,9 +1028,6 @@ func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 		EnableFingerprintUnification:         updatedSettings.EnableFingerprintUnification,
 		EnableMetadataPassthrough:            updatedSettings.EnableMetadataPassthrough,
 		EnableCCHSigning:                     updatedSettings.EnableCCHSigning,
-		BalanceLowNotifyEnabled:              updatedSettings.BalanceLowNotifyEnabled,
-		BalanceLowNotifyThreshold:            updatedSettings.BalanceLowNotifyThreshold,
-		AccountQuotaNotifyEmails:             updatedSettings.AccountQuotaNotifyEmails,
 		PaymentEnabled:                       updatedPaymentCfg.Enabled,
 		PaymentMinAmount:                     updatedPaymentCfg.MinAmount,
 		PaymentMaxAmount:                     updatedPaymentCfg.MaxAmount,
@@ -1876,3 +1848,59 @@ func (h *SettingHandler) UpdateStreamTimeoutSettings(c *gin.Context) {
 		ThresholdWindowMinutes: updatedSettings.ThresholdWindowMinutes,
 	})
 }
+
+// GetWebSearchEmulationConfig 获取 Web Search 模拟配置
+// GET /api/v1/admin/settings/web-search-emulation
+func (h *SettingHandler) GetWebSearchEmulationConfig(c *gin.Context) {
+	cfg, err := h.settingService.GetWebSearchEmulationConfig(c.Request.Context())
+	if err != nil {
+		response.ErrorFrom(c, err)
+		return
+	}
+	response.Success(c, service.SanitizeWebSearchConfig(c.Request.Context(), cfg))
+}
+
+// UpdateWebSearchEmulationConfig 更新 Web Search 模拟配置
+// PUT /api/v1/admin/settings/web-search-emulation
+func (h *SettingHandler) UpdateWebSearchEmulationConfig(c *gin.Context) {
+	var cfg service.WebSearchEmulationConfig
+	if err := c.ShouldBindJSON(&cfg); err != nil {
+		response.BadRequest(c, "Invalid request: "+err.Error())
+		return
+	}
+
+	if err := h.settingService.SaveWebSearchEmulationConfig(c.Request.Context(), &cfg); err != nil {
+		response.ErrorFrom(c, err)
+		return
+	}
+
+	// Re-read (with sanitized api keys) to return current state
+	updated, err := h.settingService.GetWebSearchEmulationConfig(c.Request.Context())
+	if err != nil {
+		response.ErrorFrom(c, err)
+		return
+	}
+	response.Success(c, service.SanitizeWebSearchConfig(c.Request.Context(), updated))
+}
+
+// TestWebSearchEmulation 测试 Web Search 搜索
+// POST /api/v1/admin/settings/web-search-emulation/test
+func (h *SettingHandler) TestWebSearchEmulation(c *gin.Context) {
+	var req struct {
+		Query string `json:"query"`
+	}
+	if err := c.ShouldBindJSON(&req); err != nil {
+		response.BadRequest(c, "Invalid request: "+err.Error())
+		return
+	}
+	if strings.TrimSpace(req.Query) == "" {
+		req.Query = "搜索今年世界大事件"
+	}
+
+	result, err := service.TestWebSearch(c.Request.Context(), req.Query)
+	if err != nil {
+		response.ErrorFrom(c, err)
+		return
+	}
+	response.Success(c, result)
+}