Refactor user detail page: split components, unify formatters

Break the 615-line UserDetail.tsx into focused sub-components
(header, stat cards, activity chart, request history, open alerts)
and extract shared utilities to lib/ (format, userChart,
enrichRequests). Promote storage load (GB/hr) to a stat card and
collapse the chart UX to a single metric picker. Add server-wide
average reference line alongside the user's own on every metric,
and link request titles to their Seerr pages.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/app/page.tsx

@@ -2,6 +2,7 @@
 
 import { useEffect, useState, useCallback, useRef } from "react";
 import { DashboardStats } from "@/lib/types";
+import { timeAgo } from "@/lib/format";
 import SummaryCards from "@/components/SummaryCards";
 import LeaderboardTable from "@/components/LeaderboardTable";
 import AlertsPanel from "@/components/AlertsPanel";
@@ -11,16 +12,6 @@ import SettingsModal from "@/components/SettingsModal";
 type Tab = "leaderboard" | "alerts";
 const LS_KEY = "oversnitch_stats";
 
-function timeAgo(iso: string): string {
-  const diff = Date.now() - new Date(iso).getTime();
-  const mins = Math.floor(diff / 60_000);
-  if (mins < 1) return "just now";
-  if (mins < 60) return `${mins}m ago`;
-  const hrs = Math.floor(mins / 60);
-  if (hrs < 24) return `${hrs}h ago`;
-  return new Date(iso).toLocaleDateString();
-}
-
 export default function Page() {
   const [tab, setTab] = useState<Tab>("leaderboard");
   const [data, setData] = useState<DashboardStats | null>(null);