feat(admin): 独立后台壳、站点分析与聊天监管，公开站拆出主题切换与访问埋点

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/service/telemetry.go

@@ -0,0 +1,88 @@
+package service
+
+import (
+	"crypto/sha256"
+	"encoding/hex"
+	"errors"
+	"regexp"
+	"strings"
+	"time"
+
+	"github.com/freefire/jiang13-bbs/model"
+	"gorm.io/gorm"
+	"gorm.io/gorm/clause"
+)
+
+var (
+	vidUUIDRe = regexp.MustCompile(`(?i)^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$`)
+)
+
+// TelemetryService 轻量页面访问埋点
+type TelemetryService struct {
+	db *gorm.DB
+}
+
+func NewTelemetryService(db *gorm.DB) *TelemetryService {
+	return &TelemetryService{db: db}
+}
+
+func todayDate() time.Time {
+	now := time.Now()
+	return time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, now.Location())
+}
+
+func hashVid(vid string) string {
+	sum := sha256.Sum256([]byte(strings.TrimSpace(strings.ToLower(vid))))
+	return hex.EncodeToString(sum[:])
+}
+
+// ValidVisitorID 校验浏览器访客 ID（UUID）
+func ValidVisitorID(vid string) bool {
+	return vidUUIDRe.MatchString(strings.TrimSpace(vid))
+}
+
+// RecordPageView 记录一次页面浏览：PV 必增；合法 vid 首次出现当日才 UV+1
+func (s *TelemetryService) RecordPageView(vid string, loggedIn bool) error {
+	day := todayDate()
+
+	err := s.db.Transaction(func(tx *gorm.DB) error {
+		var st model.SiteDailyStats
+		err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).
+			Where("date = ?", day).First(&st).Error
+		if errors.Is(err, gorm.ErrRecordNotFound) {
+			st = model.SiteDailyStats{Date: day}
+			if err := tx.Create(&st).Error; err != nil {
+				return err
+			}
+			// 重新锁住新建行
+			if err := tx.Clauses(clause.Locking{Strength: "UPDATE"}).
+				Where("date = ?", day).First(&st).Error; err != nil {
+				return err
+			}
+		} else if err != nil {
+			return err
+		}
+
+		updates := map[string]interface{}{
+			"pv":         st.PV + 1,
+			"updated_at": time.Now(),
+		}
+		if loggedIn {
+			updates["logged_in_pv"] = st.LoggedInPV + 1
+		}
+
+		if ValidVisitorID(vid) {
+			vis := model.SiteDailyVisitor{Date: day, VidHash: hashVid(vid)}
+			res := tx.Clauses(clause.OnConflict{DoNothing: true}).Create(&vis)
+			if res.Error != nil {
+				return res.Error
+			}
+			if res.RowsAffected > 0 {
+				updates["uv"] = st.UV + 1
+			}
+		}
+
+		return tx.Model(&model.SiteDailyStats{}).Where("date = ?", day).Updates(updates).Error
+	})
+	return err
+}