feat: landing analytics goals, daily bar chart, referrer tracking, contact persistence

- Add per-landing analytics goals (view/click) with admin editor toggle
- Add sticky pay button option for mobile landing pages
- Add daily purchases bar chart (created vs paid) to landing stats
- Replace single purchase count with created/paid split in stats summary
- Add referrer tracking to purchases with hostname display in stats
- Add time display to purchase cards alongside date
- Pass user timezone to stats API for correct daily grouping
- Clamp referrer (500 chars) and subid (255 chars) to backend limits
- Persist contact value per-landing-slug in localStorage
- Fire buy_success analytics goal on successful delivery
- Export USER_TIMEZONE from format utils
- Add analytics/stats translations for fa.json and zh.json locales

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/locales/zh.json

@@ -3380,7 +3380,70 @@
       "loadingPeriods": "加载中...",
       "periodDaySuffix": "天",
       "localeTab": "语言",
-      "localeHint": "切换语言以编辑该语言的文本"
+      "localeHint": "切换语言以编辑该语言的文本",
+      "discount": "折扣",
+      "discountEnabled": "启用折扣",
+      "discountPercent": "折扣 %",
+      "discountStartsAt": "开始日期",
+      "discountEndsAt": "结束日期",
+      "discountBadge": "横幅文本（可选）",
+      "discountBadgePlaceholder": "例如 春季特卖！",
+      "discountOverrides": "各套餐独立折扣",
+      "discountOverridesHint": "留空则使用全局折扣",
+      "discountPreview": "预览",
+      "discountActive": "折扣",
+      "background": "动态背景",
+      "analytics": "分析",
+      "viewGoal": "浏览目标",
+      "clickGoal": "支付点击目标",
+      "statistics": "统计",
+      "stats": {
+        "title": "落地页统计",
+        "totalPurchases": "购买次数",
+        "revenue": "收入",
+        "giftPurchases": "礼物",
+        "regularPurchases": "普通",
+        "conversionRate": "转化率",
+        "avgPurchase": "平均客单价",
+        "dailyChart": "每日购买与收入",
+        "tariffChart": "套餐分布",
+        "giftBreakdown": "礼物 vs 普通",
+        "purchases": "购买",
+        "revenueLabel": "收入",
+        "gifts": "礼物",
+        "regular": "普通",
+        "created": "已创建",
+        "successful": "成功",
+        "funnel": "漏斗",
+        "loadError": "加载统计失败",
+        "noPurchases": "无购买记录",
+        "paid": "已支付"
+      },
+      "purchases": {
+        "title": "购买记录",
+        "contact": "联系方式",
+        "recipient": "收件人",
+        "tariff": "套餐",
+        "period": "周期",
+        "days": "天",
+        "price": "价格",
+        "method": "方式",
+        "date": "日期",
+        "gift": "礼物",
+        "forSelf": "自用",
+        "allStatuses": "全部状态",
+        "status_pending": "待处理",
+        "status_paid": "已支付",
+        "status_delivered": "已交付",
+        "status_pending_activation": "待激活",
+        "status_failed": "失败",
+        "status_expired": "已过期",
+        "noPurchases": "无购买记录",
+        "showing": "显示第 {{from}}–{{to}} 条，共 {{total}} 条",
+        "page": "第 {{current}} 页，共 {{total}} 页",
+        "prev": "上一页",
+        "next": "下一页"
+      }
     },
     "infoPages": {
       "title": "信息页面",