feat: v2 dashboard — React + Vite parallel implementation

New modern dashboard at /v2 running alongside the existing UI at /.
Same backend, same APIs, same WebSocket — zero backend changes.

Stack: React 19 + Vite + TypeScript + Recharts
Source: frontend/ — build output: static/v2/

Phase 1 delivers:
- Character overview cards in a responsive CSS Grid
  - Live HP/Stamina/Mana bars via WebSocket vitals
  - Kills/hr, total kills, deaths, session uptime
  - VTank state badge (Combat/Nav/Idle)
  - Location coordinates
  - Click to expand: combat stats, prismatic count, CPU/RAM
- Global stats header: active chars, total kills, total rares, server health
- WebSocket hook with auto-reconnect
- HTTP poll fallback for initial load + server health
- Mobile responsive (single column on narrow screens)
- Dark theme matching the MosswartOverlord palette

Build: cd frontend && npm run build
Access: /v2 (served by existing NoCacheStaticFiles mount)

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

frontend/src/hooks/useWebSocket.ts

@@ -0,0 +1,44 @@
+import { useEffect, useRef, useCallback } from 'react';
+import { wsUrl } from '../api/client';
+import type { WSMessage } from '../types';
+
+type MessageHandler = (msg: WSMessage) => void;
+
+export function useWebSocket(onMessage: MessageHandler) {
+  const wsRef = useRef<WebSocket | null>(null);
+  const reconnectTimer = useRef<number>(0);
+  const onMessageRef = useRef(onMessage);
+  onMessageRef.current = onMessage;
+
+  const connect = useCallback(() => {
+    if (wsRef.current?.readyState === WebSocket.OPEN) return;
+
+    const ws = new WebSocket(wsUrl());
+    wsRef.current = ws;
+
+    ws.addEventListener('message', (evt) => {
+      try {
+        const msg = JSON.parse(evt.data) as WSMessage;
+        onMessageRef.current(msg);
+      } catch { /* ignore parse errors */ }
+    });
+
+    ws.addEventListener('close', () => {
+      wsRef.current = null;
+      reconnectTimer.current = window.setTimeout(connect, 2000);
+    });
+
+    ws.addEventListener('error', () => {
+      ws.close();
+    });
+  }, []);
+
+  useEffect(() => {
+    connect();
+    return () => {
+      clearTimeout(reconnectTimer.current);
+      wsRef.current?.close();
+      wsRef.current = null;
+    };
+  }, [connect]);
+}