feat: Soundboard Plugin + Radio Globe Fixes

- Add Soundboard plugin (full Jukebox port): server + frontend + CSS
- Fix Radio Globe: swap geo coords (API returns [lng,lat] not [lat,lng])
- Fix Radio stations showing "Unbekannt": use item.page.title + fix channel ID regex
- Add DirectMessages + MessageContent intents for DM commands
- Register SoundboardTab in App.tsx with scoped theme/card-size CSS vars

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

server/src/core/discord.ts

@@ -1,10 +1,13 @@
-import { Client, GatewayIntentBits } from 'discord.js';
+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;