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/plugin.ts

@@ -0,0 +1,39 @@
+import { Client } from 'discord.js';
+import express from 'express';
+
+export interface Plugin {
+  name: string;
+  version: string;
+  description: string;
+
+  /** Called once when plugin is loaded */
+  init(ctx: PluginContext): Promise<void>;
+
+  /** Called when Discord client is ready */
+  onReady?(ctx: PluginContext): Promise<void>;
+
+  /** Called to register Express routes */
+  registerRoutes?(app: express.Application, ctx: PluginContext): void;
+
+  /** Called to build SSE snapshot data for new clients */
+  getSnapshot?(ctx: PluginContext): Record<string, any>;
+
+  /** Called on graceful shutdown */
+  destroy?(ctx: PluginContext): Promise<void>;
+}
+
+export interface PluginContext {
+  client: Client;
+  dataDir: string;
+}
+
+const loadedPlugins: Plugin[] = [];
+
+export function registerPlugin(plugin: Plugin): void {
+  loadedPlugins.push(plugin);
+  console.log(`[Plugin] Registered: ${plugin.name} v${plugin.version}`);
+}
+
+export function getPlugins(): Plugin[] {
+  return [...loadedPlugins];
+}