Per-player playtime tracking + sparkline hover tooltips

- New GET /api/players/playtime (authed): reads each vanilla stats file
  under /home/minecraft/server/world/stats and maps uuid→name via
  usercache.json. Returns playtime in ticks and hours, plus file mtime
  as "last seen". Memoized 60s via lib/cache#memoAsync.
- New PlaytimeLeaderboard card in the Players tab:
    - Rank, avatar (click → PlayerDrawer), relative last-seen, hours.
    - Top 10 by default with toggle to show all; combined hours badge.
- PlayerDrawer surfaces the player's total hours + last-seen using the
  same cached playtime query, plus fills in UUID if the player is not
  in ops/whitelist/banned.
- lib/time.ts: formatHours() — minutes under 1h, "H.Hh" under a day,
  "Dd Hh" above.
- Analytics sparklines gain hover/touch tooltips:
    - Timestamps threaded through from each MetricEntry.
    - SVG overlay captures onMouseMove/onTouchMove, computes nearest
      index by x, draws a dashed guide line + focus dot.
    - Floating tooltip shows HH:MM + formatted value with unit; edge
      clamping keeps it in-frame at the extremes.
    - Per-chart formatValue so RAM shows GB, CPU 0 decimals, Players
      integer, TPS 1 decimal. Keeps the peak-player marker intact.

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

components/PlayerManager.tsx

@@ -15,6 +15,7 @@ import {
   CardTitle,
 } from "@/components/ui/card";
 import { PlayerAvatar } from "@/components/PlayerAvatar";
+import { PlaytimeLeaderboard } from "@/components/PlaytimeLeaderboard";
 
 type PlayerData = {
   ops: { name: string; uuid: string; level: number }[];
@@ -127,6 +128,8 @@ export function PlayerManager() {
   };
 
   return (
+    <div className="space-y-4 sm:space-y-6">
+      <PlaytimeLeaderboard />
     <Card>
       <CardHeader>
         <CardTitle>Player Management</CardTitle>
@@ -296,5 +299,6 @@ export function PlayerManager() {
         )}
       </CardContent>
     </Card>
+    </div>
   );
 }