feat: add admin panel with Discord OAuth and dashboard

Adds a React admin panel (panel/) with Discord OAuth2 login,
live dashboard via WebSocket, and settings/management pages.
Includes Docker build support, Vite proxy config for dev,
game_settings migration, and open-redirect protection on auth callback.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -4,6 +4,7 @@
   "module": "bot/index.ts",
   "type": "module",
   "private": true,
+  "workspaces": ["panel"],
   "devDependencies": {
     "@types/bun": "latest",
     "drizzle-kit": "^0.31.8"
@@ -30,6 +31,8 @@
     "test": "bash shared/scripts/test-sequential.sh",
     "test:ci": "bash shared/scripts/test-sequential.sh --integration",
     "test:simulate-ci": "bash shared/scripts/simulate-ci.sh",
+    "panel:dev": "cd panel && bun run dev",
+    "panel:build": "cd panel && bun run build",
     "deploy": "bash shared/scripts/deploy.sh",
     "deploy:remote": "bash shared/scripts/deploy-remote.sh",
     "setup-server": "bash shared/scripts/setup-server.sh",