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/.gitignore

@@ -0,0 +1,2 @@
+node_modules/
+dist/