feat(observability): delivery metrics, admin metrics/delivery endpoints, admin API route wiring

app/composables/useI18n.ts

@@ -17,6 +17,19 @@ const en: Dict = {
   "tab.groups": "Groups",
   "tab.logs": "Send Logs",
   "tab.audit": "Audit Log",
+  "tab.metrics": "Metrics",
+  "metrics.title": "Delivery Metrics",
+  "metrics.refresh": "Refresh",
+  "metrics.total": "Total",
+  "metrics.ok": "OK",
+  "metrics.failed": "Failed",
+  "metrics.failureRate": "Failure rate",
+  "metrics.avgDuration": "Avg duration",
+  "metrics.avgAttempts": "Avg attempts",
+  "metrics.byPlatform": "By platform",
+  "metrics.byEvent": "By event",
+  "metrics.recentFailures": "Recent failures",
+  "metrics.empty": "No delivery data yet",
   "status.loading": "loading",
   "status.connected": "connected",
   "kpi.groups": "GROUPS",
@@ -281,6 +294,19 @@ const zh: Dict = {
   "tab.groups": "分组",
   "tab.logs": "发送日志",
   "tab.audit": "审计日志",
+  "tab.metrics": "指标",
+  "metrics.title": "投递指标",
+  "metrics.refresh": "刷新",
+  "metrics.total": "总计",
+  "metrics.ok": "成功",
+  "metrics.failed": "失败",
+  "metrics.failureRate": "失败率",
+  "metrics.avgDuration": "平均耗时",
+  "metrics.avgAttempts": "平均尝试次数",
+  "metrics.byPlatform": "按平台",
+  "metrics.byEvent": "按事件",
+  "metrics.recentFailures": "最近失败",
+  "metrics.empty": "暂无投递数据",
   "status.loading": "加载中",
   "status.connected": "已连接",
   "kpi.groups": "分组",