feat(account): 支持账号级别拦截预热请求

- 新增 intercept_warmup_requests 配置项，存储在 credentials 字段
- 启用后，标题生成、Warmup 等预热请求返回 mock 响应，不消耗上游 token
- 前端支持所有账号类型（OAuth、Setup Token、API Key）的开关配置
- 修复 OAuth 凭证刷新时丢失非 token 配置的问题

backend/internal/handler/admin/account_handler.go

@@ -241,16 +241,20 @@ func (h *AccountHandler) Refresh(c *gin.Context) {
 		return
 	}
 
-	// Update account credentials
-	newCredentials := map[string]interface{}{
-		"access_token":  tokenInfo.AccessToken,
-		"token_type":    tokenInfo.TokenType,
-		"expires_in":    tokenInfo.ExpiresIn,
-		"expires_at":    tokenInfo.ExpiresAt,
-		"refresh_token": tokenInfo.RefreshToken,
-		"scope":         tokenInfo.Scope,
+	// Copy existing credentials to preserve non-token settings (e.g., intercept_warmup_requests)
+	newCredentials := make(map[string]interface{})
+	for k, v := range account.Credentials {
+		newCredentials[k] = v
 	}
 
+	// Update token-related fields
+	newCredentials["access_token"] = tokenInfo.AccessToken
+	newCredentials["token_type"] = tokenInfo.TokenType
+	newCredentials["expires_in"] = tokenInfo.ExpiresIn
+	newCredentials["expires_at"] = tokenInfo.ExpiresAt
+	newCredentials["refresh_token"] = tokenInfo.RefreshToken
+	newCredentials["scope"] = tokenInfo.Scope
+
 	updatedAccount, err := h.adminService.UpdateAccount(c.Request.Context(), accountID, &service.UpdateAccountInput{
 		Credentials: newCredentials,
 	})

backend/internal/handler/gateway_handler.go

@@ -7,6 +7,7 @@ import (
 	"io"
 	"log"
 	"net/http"
+	"strings"
 	"time"
 
 	"sub2api/internal/middleware"
@@ -127,6 +128,16 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 		return
 	}
 
+	// 检查预热请求拦截（在账号选择后、转发前检查）
+	if account.IsInterceptWarmupEnabled() && isWarmupRequest(body) {
+		if req.Stream {
+			sendMockWarmupStream(c, req.Model)
+		} else {
+			sendMockWarmupResponse(c, req.Model)
+		}
+		return
+	}
+
 	// 3. 获取账号并发槽位
 	accountReleaseFunc, err := h.acquireAccountSlotWithWait(c, account, req.Stream, &streamStarted)
 	if err != nil {
@@ -489,3 +500,89 @@ func (h *GatewayHandler) CountTokens(c *gin.Context) {
 		return
 	}
 }
+
+// isWarmupRequest 检测是否为预热请求（标题生成、Warmup等）
+func isWarmupRequest(body []byte) bool {
+	// 快速检查：如果body不包含关键字，直接返回false
+	bodyStr := string(body)
+	if !strings.Contains(bodyStr, "title") && !strings.Contains(bodyStr, "Warmup") {
+		return false
+	}
+
+	// 解析完整请求
+	var req struct {
+		Messages []struct {
+			Content []struct {
+				Type string `json:"type"`
+				Text string `json:"text"`
+			} `json:"content"`
+		} `json:"messages"`
+		System []struct {
+			Text string `json:"text"`
+		} `json:"system"`
+	}
+	if err := json.Unmarshal(body, &req); err != nil {
+		return false
+	}
+
+	// 检查 messages 中的标题提示模式
+	for _, msg := range req.Messages {
+		for _, content := range msg.Content {
+			if content.Type == "text" {
+				if strings.Contains(content.Text, "Please write a 5-10 word title for the following conversation:") ||
+					content.Text == "Warmup" {
+					return true
+				}
+			}
+		}
+	}
+
+	// 检查 system 中的标题提取模式
+	for _, system := range req.System {
+		if strings.Contains(system.Text, "nalyze if this message indicates a new conversation topic. If it does, extract a 2-3 word title") {
+			return true
+		}
+	}
+
+	return false
+}
+
+// sendMockWarmupStream 发送流式 mock 响应（用于预热请求拦截）
+func sendMockWarmupStream(c *gin.Context, model string) {
+	c.Header("Content-Type", "text/event-stream")
+	c.Header("Cache-Control", "no-cache")
+	c.Header("Connection", "keep-alive")
+	c.Header("X-Accel-Buffering", "no")
+
+	events := []string{
+		`event: message_start` + "\n" + `data: {"message":{"content":[],"id":"msg_mock_warmup","model":"` + model + `","role":"assistant","stop_reason":null,"stop_sequence":null,"type":"message","usage":{"input_tokens":10,"output_tokens":0}},"type":"message_start"}`,
+		`event: content_block_start` + "\n" + `data: {"content_block":{"text":"","type":"text"},"index":0,"type":"content_block_start"}`,
+		`event: content_block_delta` + "\n" + `data: {"delta":{"text":"New","type":"text_delta"},"index":0,"type":"content_block_delta"}`,
+		`event: content_block_delta` + "\n" + `data: {"delta":{"text":" Conversation","type":"text_delta"},"index":0,"type":"content_block_delta"}`,
+		`event: content_block_stop` + "\n" + `data: {"index":0,"type":"content_block_stop"}`,
+		`event: message_delta` + "\n" + `data: {"delta":{"stop_reason":"end_turn","stop_sequence":null},"type":"message_delta","usage":{"input_tokens":10,"output_tokens":2}}`,
+		`event: message_stop` + "\n" + `data: {"type":"message_stop"}`,
+	}
+
+	for _, event := range events {
+		_, _ = c.Writer.WriteString(event + "\n\n")
+		c.Writer.Flush()
+		time.Sleep(20 * time.Millisecond)
+	}
+}
+
+// sendMockWarmupResponse 发送非流式 mock 响应（用于预热请求拦截）
+func sendMockWarmupResponse(c *gin.Context, model string) {
+	c.JSON(http.StatusOK, gin.H{
+		"id":      "msg_mock_warmup",
+		"type":    "message",
+		"role":    "assistant",
+		"model":   model,
+		"content": []gin.H{{"type": "text", "text": "New Conversation"}},
+		"stop_reason": "end_turn",
+		"usage": gin.H{
+			"input_tokens":  10,
+			"output_tokens": 2,
+		},
+	})
+}