Initial commit: Gaming Hub foundation

Plugin-based Discord bot framework with web frontend:
- Core: Discord.js client, SSE broadcast, JSON persistence
- Plugin system: lifecycle hooks (init, onReady, routes, snapshot, destroy)
- Web: React 19 + Vite 6 + TypeScript, tab-based navigation
- Docker: multi-stage build (Node 24, static ffmpeg, yt-dlp)
- GitLab CI: Kaniko with LAN registry caching

Ready for plugin development.

server/src/core/sse.ts

@@ -0,0 +1,22 @@
+import { Response } from 'express';
+
+const sseClients = new Set<Response>();
+
+export function addSSEClient(res: Response): void {
+  sseClients.add(res);
+}
+
+export function removeSSEClient(res: Response): void {
+  sseClients.delete(res);
+}
+
+export function sseBroadcast(data: Record<string, any>): void {
+  const msg = `data: ${JSON.stringify(data)}\n\n`;
+  for (const c of sseClients) {
+    try { c.write(msg); } catch { sseClients.delete(c); }
+  }
+}
+
+export function getSSEClientCount(): number {
+  return sseClients.size;
+}