feat: 站点访问统计与可配置侧边栏组件

- 新增访问统计：visitstats 服务与查询、visit_capture 中间件、爬虫/来源识别、管理端 analytics 页面
- 新增侧边栏：sidebar 服务与 handler、管理端 sidebar 配置页、前端侧边栏组件
- 新增 widget 嵌入代码生成（widgetCode）与 widgetApi
- 遥测逻辑迁移至 handler 层，删除 service/telemetry
- env 示例补充 Docker 部署可信代理 IP 说明

backend/service/visitstats_test.go

@@ -0,0 +1,46 @@
+package service
+
+import (
+	"testing"
+	"time"
+
+	"github.com/freefire/jiang13-bbs/model"
+)
+
+func TestSummarizePageviews(t *testing.T) {
+	day := time.Date(2026, 9, 24, 0, 0, 0, 0, time.Local)
+	at := func(hour int) time.Time { return day.Add(time.Duration(hour) * time.Hour) }
+
+	events := []model.VisitEvent{
+		{Kind: model.VisitKindPageview, CreatedAt: at(9), UserID: 1, VidHash: "aaa"},
+		{Kind: model.VisitKindPageview, CreatedAt: at(9), VidHash: "aaa"}, // 同 vid 同日：去重
+		{Kind: model.VisitKindPageview, CreatedAt: at(10), VidHash: "bbb"},
+		{Kind: model.VisitKindBot, CreatedAt: at(9), VidHash: "aaa"},   // bot 不计
+		{Kind: model.VisitKindProbe, CreatedAt: at(9), VidHash: "bbb"}, // probe 不计
+	}
+	out := summarizePageviews(events)
+	d, ok := out[day]
+	if !ok {
+		t.Fatal("缺少当日聚合")
+	}
+	if d.PV != 3 {
+		t.Errorf("PV = %d, want 3", d.PV)
+	}
+	if d.LoggedInPV != 1 {
+		t.Errorf("LoggedInPV = %d, want 1", d.LoggedInPV)
+	}
+	if len(d.VidHashes) != 2 {
+		t.Errorf("UV 候选 = %d, want 2", len(d.VidHashes))
+	}
+}
+
+func TestHashVisitorID(t *testing.T) {
+	a := HashVisitorID("  ABcd1234-0000-0000-0000-000000000000 ")
+	b := HashVisitorID("abcd1234-0000-0000-0000-000000000000")
+	if a != b {
+		t.Error("大小写/空白应归一后哈希一致")
+	}
+	if len(a) != 64 {
+		t.Errorf("哈希长度 = %d, want 64", len(a))
+	}
+}