Feat: Multi-bot support - separate Discord bot per plugin

Each plugin gets its own Discord client and token:
- DISCORD_TOKEN_JUKEBOX (fallback: DISCORD_TOKEN) → Soundboard
- DISCORD_TOKEN_RADIO → Radio

discord.ts: factory createClient() instead of singleton
plugin.ts: per-plugin context storage via registerPlugin(p, ctx)
index.ts: creates/logins/shutdowns multiple bots independently

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

server/src/core/discord.ts

@@ -1,13 +1,14 @@
 import { Client, GatewayIntentBits, Partials } from 'discord.js';
 
-const client = new Client({
-  intents: [
-    GatewayIntentBits.Guilds,
-    GatewayIntentBits.GuildVoiceStates,
-    GatewayIntentBits.DirectMessages,
-    GatewayIntentBits.MessageContent,
-  ],
-  partials: [Partials.Channel],
-});
-
-export default client;
+/** Create a new Discord client instance (one per bot token). */
+export function createClient(): Client {
+  return new Client({
+    intents: [
+      GatewayIntentBits.Guilds,
+      GatewayIntentBits.GuildVoiceStates,
+      GatewayIntentBits.DirectMessages,
+      GatewayIntentBits.MessageContent,
+    ],
+    partials: [Partials.Channel],
+  });
+}

server/src/core/plugin.ts

@@ -30,9 +30,11 @@ export interface PluginContext {
 }
 
 const loadedPlugins: Plugin[] = [];
+const pluginContexts = new Map<string, PluginContext>();
 
-export function registerPlugin(plugin: Plugin): void {
+export function registerPlugin(plugin: Plugin, ctx: PluginContext): void {
   loadedPlugins.push(plugin);
+  pluginContexts.set(plugin.name, ctx);
   console.log(`[Plugin] Registered: ${plugin.name} v${plugin.version}`);
 }
 
@@ -40,6 +42,10 @@ export function getPlugins(): Plugin[] {
   return [...loadedPlugins];
 }
 
+export function getPluginCtx(pluginName: string): PluginContext | undefined {
+  return pluginContexts.get(pluginName);
+}
+
 // ── Voice claim system ──
 // Only one plugin can use voice per guild. When a new plugin claims voice,
 // the previous claimant's cleanup callback is invoked automatically.