Rich per-player stats + pick-your-metric leaderboard

- lib/player-stats.ts: single computePlayerStats() reads every
  world/stats/<uuid>.json plus world/advancements/<uuid>.json and joins
  with usercache.json. Returns a flat PlayerStats record per player:
  playtime, longest life, mob/player kills, deaths, K/D, damage dealt
  and taken (HP-scaled), blocks mined, items used / crafted / picked up
  (+ unique), distance (summed across all _one_cm stats), chest opens,
  nether/end trips, villager trades, fish caught, animals bred, and
  advancements (non-recipe) / recipes unlocked.
- New GET /api/players/stats (authed, 60s memo). Existing
  /api/players/playtime now returns a thin projection of the same
  computed data (shared cache key keeps both endpoints cheap).
- New components/Leaderboard.tsx with a metric select grouped into
  Time / Combat / World / Exploration / Progression / Economy (22
  metrics). Sorts descending, top 10 with "show all" toggle, smart
  number formatting (1.2k / 3.4M / HP / km). Replaces the old
  PlaytimeLeaderboard in the Players tab.
- PlayerDrawer upgraded: uses the full stats payload, shows small
  tiles for Kills / Deaths / K/D / Advs / Mined / Crafted / Distance
  alongside Playtime + Last seen.

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

app/api/players/stats/route.ts

@@ -0,0 +1,28 @@
+import { NextResponse } from "next/server";
+import { auth } from "@/lib/auth";
+import { memoAsync } from "@/lib/cache";
+import { computePlayerStats } from "@/lib/player-stats";
+
+export const dynamic = "force-dynamic";
+export const runtime = "nodejs";
+
+export async function GET() {
+  const session = await auth();
+  if (!session) {
+    return NextResponse.json({ error: "Unauthorized" }, { status: 403 });
+  }
+
+  try {
+    const data = await memoAsync("players:stats", 60_000, async () =>
+      computePlayerStats()
+    );
+    return NextResponse.json(data, {
+      headers: { "Cache-Control": "private, max-age=60" },
+    });
+  } catch (e) {
+    return NextResponse.json(
+      { error: (e as Error).message },
+      { status: 500 }
+    );
+  }
+}