feat(ai): 全站 AI 助手浮窗(参考 FlowStack 右下角浮空设计)

- POST /ai/chat:多轮对话(messages 透传)+ 页面上下文注入 —— 前端带当前路径,
  后端自动附加该数据源近 15 分钟轻量日志摘要(总量/Top3 应用/告警命中),
  追问「这个报错什么原因」有数据依据;脱敏/每日配额/Pro 闸门与整页分析共用
- AiAssistant 浮球+浮窗挂 Layout:仅 admin+Pro 渲染;消息气泡、Enter 发送、
  上下文随路由自动采集;免费版不显示

backend/controllers/ai.go

@@ -153,3 +153,31 @@ func (ctrl *AIController) GetRun(c *gin.Context) {
 	}
 	utils.Success(c, run)
 }
+
+// Chat 全站 AI 助手浮窗(多轮对话 + 页面上下文注入;Pro 闸门)
+func (ctrl *AIController) Chat(c *gin.Context) {
+	var req struct {
+		SourceID     uint                   `json:"sourceId"`
+		History      []services.ChatMessage `json:"history" binding:"required,min=1,max=40"`
+		Page         string                 `json:"page"`
+		RangeMinutes int                    `json:"rangeMinutes"`
+	}
+	if !utils.BindAndValidate(c, &req) {
+		return
+	}
+	cfg := services.GetAIConfig()
+	var src *models.LogSource
+	if req.SourceID > 0 {
+		src = services.GetLogSource(req.SourceID)
+	}
+	rangeMinutes := req.RangeMinutes
+	if rangeMinutes <= 0 || rangeMinutes > 120 {
+		rangeMinutes = 15
+	}
+	reply, err := services.RunAIChat(c.Request.Context(), cfg, src, c.GetUint("userId"), c.GetString("role") == "admin", req.History, req.Page, rangeMinutes)
+	if err != nil {
+		utils.Error(c, 400, err.Error())
+		return
+	}
+	utils.Success(c, gin.H{"reply": reply})
+}

backend/routers/router.go

@@ -131,6 +131,7 @@ func SetupRouter() *gin.Engine {
 		ai.PUT("/config", middleware.AdminAuth(), aiCtrl.SaveConfig)
 		ai.POST("/config/test", middleware.AdminAuth(), aiCtrl.TestConfig)
 		ai.POST("/analyze", middleware.RequirePro(), aiCtrl.Analyze)
+		ai.POST("/chat", middleware.RequirePro(), aiCtrl.Chat)
 		ai.GET("/runs", aiCtrl.ListRuns)
 		ai.GET("/runs/:id", aiCtrl.GetRun)
 	}

backend/services/ai_provider.go

@@ -6,6 +6,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"io"
+	"lokistack/repository"
 	"net/http"
 	"strings"
 	"time"
@@ -126,3 +127,70 @@ func TestAIConnection(cfg models.AIConfig) (string, error) {
 	}
 	return strings.TrimSpace(reply), nil
 }
+
+// ChatMessage 浮窗助手的多轮消息(user/assistant 交替)
+type ChatMessage struct {
+	Role    string `json:"role" binding:"required,oneof=user assistant"`
+	Content string `json:"content" binding:"required"`
+}
+
+// RunAIChat 全站 AI 助手浮窗:多轮对话 + 当前页面上下文注入(轻量信号摘要)。
+// 与整页分析共享配置/配额/脱敏/Pro 闸门;context 里的 sourceId 可选,带了就注入日志摘要。
+func RunAIChat(ctx context.Context, cfg models.AIConfig, src *models.LogSource, userID uint, admin bool, history []ChatMessage, page string, rangeMinutes int) (string, error) {
+	if !cfg.Enabled {
+		return "", fmt.Errorf("AI 未启用:请先在「智能运维 → 模型配置」中开启并保存")
+	}
+	if cfg.DailyTokenCap > 0 && AITokenUsedToday(userID) >= cfg.DailyTokenCap {
+		return "", fmt.Errorf("今日 AI 用量已达上限,明天再试或调整上限")
+	}
+
+	system := "你是 LokiStack 日志平台的运维助手。回答简明、面向排查行动;不确定就说不确定。"
+	if src != nil && rangeMinutes > 0 {
+		end := time.Now()
+		from := end.Add(-time.Duration(rangeMinutes) * time.Minute)
+		if bundle, err := CollectAISignals(ctx, src, userID, admin, from, end, ""); err == nil {
+			system += "\n\n当前用户正在查看 " + page + " 页,近 " + fmt.Sprintf("%d", rangeMinutes) + " 分钟的日志概况:总量 " +
+				fmt.Sprintf("%d", bundle.TotalEntries) + " 条(估算)"
+			if len(bundle.Apps) > 0 {
+				system += ",Top 应用:"
+				for i, a := range bundle.Apps {
+					if i >= 3 {
+						break
+					}
+					system += fmt.Sprintf(" %s(%d)", a.App, a.Entries)
+				}
+			}
+			if len(bundle.Alerts) > 0 {
+				system += ";存在告警命中"
+			}
+		}
+	}
+
+	msgs := []aiMessage{{Role: "system", Content: system}}
+	for _, m := range history {
+		msgs = append(msgs, aiMessage{Role: m.Role, Content: m.Content})
+	}
+	// 脱敏:用户消息里的敏感串同样替换
+	if cfg.RedactExtra != nil {
+		for i := range msgs {
+			msgs[i].Content = RedactTextOnly(msgs[i].Content, cfg.RedactExtra)
+		}
+	}
+	reply, promptTokens, completionTokens, err := aiChat(ctx, cfg, msgs)
+	if err != nil {
+		return "", err
+	}
+	// 计入每日配额:落一条 chat 类型用量记录
+	db := repository.GetDB()
+	if db != nil {
+		db.Lock()
+		db.AIAnalysisRuns = append(db.AIAnalysisRuns, models.AIAnalysisRun{
+			UserID: userID, Username: "chat", SourceID: 0, SourceName: page,
+			Status: "chat", PromptTokens: promptTokens, CompletionTokens: completionTokens,
+			CreatedAt: time.Now(),
+		})
+		db.RequestSave()
+		db.Unlock()
+	}
+	return reply, nil
+}