feat: 用户端访问足迹统计（IP 去重 UV/PV）

- 后端 Visit 模型(date+ip 唯一索引)：POST /api/track 埋点(ClientIP upsert，pv+1)，GET /api/admin/visits 每日 UV/PV 统计
- web 每会话上报一次访问(sessionStorage 防重)，IP 由后端去重
- admin 访问统计页：侧边栏入口 + 今日/近N天 UV·PV 卡片 + 每日柱状趋势(自绘无依赖) + 7/30/90 天切换

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/internal/handler/visit.go

@@ -0,0 +1,89 @@
+package handler
+
+import (
+	"strconv"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"gorm.io/gorm"
+	"gorm.io/gorm/clause"
+
+	"git.sundynix.cn/Blizzard/sundynix-site/server/internal/model"
+	"git.sundynix.cn/Blizzard/sundynix-site/server/internal/pkg/resp"
+)
+
+// VisitHandler 访问足迹：用户端埋点 + 管理端统计。
+type VisitHandler struct {
+	db *gorm.DB
+}
+
+func NewVisitHandler(db *gorm.DB) *VisitHandler {
+	return &VisitHandler{db: db}
+}
+
+// Track POST /api/track — 用户端埋点上报（免登录）。
+// 按 (今天, ClientIP) upsert：已存在则 pv+1，否则插入 pv=1。
+func (h *VisitHandler) Track(c *gin.Context) {
+	ip := c.ClientIP()
+	if ip == "" {
+		ip = "unknown"
+	}
+	visit := model.Visit{
+		Date: time.Now().Format("2006-01-02"),
+		IP:   ip,
+		PV:   1,
+	}
+	h.db.Clauses(clause.OnConflict{
+		Columns: []clause.Column{{Name: "date"}, {Name: "ip"}},
+		DoUpdates: clause.Assignments(map[string]any{
+			"pv":         gorm.Expr("pv + 1"),
+			"updated_at": time.Now(),
+		}),
+	}).Create(&visit)
+	resp.OK(c, nil)
+}
+
+type dailyRow struct {
+	Date string `json:"date"`
+	UV   int64  `json:"uv"`
+	PV   int64  `json:"pv"`
+}
+
+// Stats GET /api/admin/visits?days=30 — 近 N 天每日 UV/PV。
+func (h *VisitHandler) Stats(c *gin.Context) {
+	days := 30
+	if v := c.Query("days"); v != "" {
+		if n, err := strconv.Atoi(v); err == nil && n > 0 && n <= 365 {
+			days = n
+		}
+	}
+	since := time.Now().AddDate(0, 0, -(days - 1)).Format("2006-01-02")
+	today := time.Now().Format("2006-01-02")
+
+	var rows []dailyRow
+	h.db.Model(&model.Visit{}).
+		Select("date, count(*) as uv, coalesce(sum(pv), 0) as pv").
+		Where("date >= ?", since).
+		Group("date").
+		Order("date").
+		Scan(&rows)
+
+	var totalUV, totalPV, todayUV, todayPV int64
+	for _, r := range rows {
+		totalUV += r.UV
+		totalPV += r.PV
+		if r.Date == today {
+			todayUV = r.UV
+			todayPV = r.PV
+		}
+	}
+
+	resp.OK(c, gin.H{
+		"daily":    rows,
+		"total_uv": totalUV,
+		"total_pv": totalPV,
+		"today_uv": todayUV,
+		"today_pv": todayPV,
+		"days":     days,
+	})
+}

server/internal/model/visit.go

@@ -0,0 +1,10 @@
+package model
+
+// Visit 用户端访问记录，按 (date, ip) 去重：每行代表某 IP 某天来过（UV）；
+// pv 记该 IP 当天访问次数。表名 sundynix_visit。
+type Visit struct {
+	BaseModel
+	Date string `gorm:"size:10;uniqueIndex:uk_date_ip" json:"date"`
+	IP   string `gorm:"size:64;uniqueIndex:uk_date_ip" json:"ip"`
+	PV   int64  `json:"pv"`
+}

server/internal/router/router.go

@@ -30,6 +30,8 @@ func New(db *gorm.DB) (*gin.Engine, error) {
 		api.GET("/posts/:slug", posts.Get)
 
 		api.GET("/releases/latest", handler.NewReleaseHandler().Latest)
+
+		api.POST("/track", handler.NewVisitHandler(db).Track)
 	}
 
 	// RSS 订阅源（页脚 RSS 链接指向这里）
@@ -43,6 +45,7 @@ func New(db *gorm.DB) (*gin.Engine, error) {
 	{
 		posts := handler.NewAdminPostHandler(db)
 		adminAPI.GET("/stats", posts.Stats)
+		adminAPI.GET("/visits", handler.NewVisitHandler(db).Stats)
 		adminAPI.GET("/posts", posts.List)
 		adminAPI.POST("/posts", posts.Create)
 		adminAPI.GET("/posts/:id", posts.Get)

server/internal/store/db.go

@@ -34,7 +34,7 @@ func Open(dsn string) (*gorm.DB, error) {
 	if err != nil {
 		return nil, err
 	}
-	if err := db.AutoMigrate(&model.Post{}); err != nil {
+	if err := db.AutoMigrate(&model.Post{}, &model.Visit{}); err != nil {
 		return nil, err
 	}
 	if err := seed(db); err != nil {