SSE events bridge, PWA service worker, offline banner, lazy admin tabs

- New /api/events SSE endpoint (authed): pushes status every 5s and chat
  on log-file mtime change (~1.5s poll). Heartbeat every 15s, hard-caps
  each stream at 10min so the browser gets a clean auth refresh on
  reconnect. Auto-aborts on client disconnect.
- Factored shared helpers out of the existing routes:
  - lib/server-status.ts (probeStatus, reused by /api/status + SSE)
  - lib/chat-log.ts (parseLogLine, readChatMessages, logMtime, reused by
    /api/chat + SSE)
- EventsBridge client (mounted in Providers) opens one EventSource per
  authed session and writes live data into the TanStack Query cache for
  ["status"] and ["chat"] — no refactor needed in consuming components,
  they keep reading their usual query keys.
- Now that SSE pushes updates, polling intervals bumped: StatusCard and
  ServerControls 10s -> 60s, ChatBridge 5s -> 30s. SSE handles realtime,
  polling is safety fallback.
- OfflineBanner: sticky amber bar when navigator.onLine flips false.
- PWA: minimal public/sw.js with shell + asset cache (network-first for
  HTML, stale-while-revalidate for static assets, never touches /api/*
  or text/event-stream). ServiceWorkerRegister client registers it in
  production only.
- AdminTabs now uses next/dynamic with skeleton fallbacks for Players /
  Chat / Mods / Backups / Logs, keeping initial /admin bundle smaller.

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

components/OfflineBanner.tsx

@@ -0,0 +1,32 @@
+"use client";
+
+import { useEffect, useState } from "react";
+
+export function OfflineBanner() {
+  const [online, setOnline] = useState(true);
+
+  useEffect(() => {
+    if (typeof navigator === "undefined") return;
+    setOnline(navigator.onLine);
+    const on = () => setOnline(true);
+    const off = () => setOnline(false);
+    window.addEventListener("online", on);
+    window.addEventListener("offline", off);
+    return () => {
+      window.removeEventListener("online", on);
+      window.removeEventListener("offline", off);
+    };
+  }, []);
+
+  if (online) return null;
+
+  return (
+    <div
+      role="status"
+      aria-live="polite"
+      className="sticky top-0 z-30 w-full bg-amber-500/20 border-b border-amber-500/30 text-amber-200 text-xs sm:text-sm px-3 py-1.5 text-center backdrop-blur"
+    >
+      You&apos;re offline — showing cached data. Live updates will resume automatically.
+    </div>
+  );
+}