refactor: remove voice/recording/media features from frontend + prune lockfiles

- Delete pages: (dashboard)/{recordings,voice,media}/ incl. view.tsx
- Delete components/{voice,media}, hooks/{use-voice,use-recordings,use-media},
  lib/audio/ (mic-transmit, pcm-player, wav), api/{voice,recordings,media},
  types/{voice,recording,media}, lib/hash.ts
- Cut nav tiles (Active Voice Stages, Voice Recording Archive) from dashboard,
  MiniPlayer from ambient-app, hooks/types barrel exports, WS voice/media events
- Re-home guilds + textChannels to messages oRPC router (DB-derived) so the
  messages page picker keeps working; guild-picker simplified to text-only
- Clean Channel/AppConfig types of voice remnants
- Delete infra/docker/recordings/ + 11 voice/recording/video spec docs
- pnpm install: prune direct voice deps from gateway + backend lockfiles
  (prism-media/opusscript remain only as transitive discord.js deps)

services/backend/src/orpc/router.ts

@@ -69,6 +69,10 @@ const dashboardRouter = {
 
 // ── Messages ─────────────────────────────────────────────────────
 const messagesRouter = {
+  guilds: os.handler(() => messagesService.getGuilds()),
+  textChannels: os
+    .input(z.object({ guildId: z.string() }))
+    .handler(({ input }) => messagesService.getTextChannels(input.guildId)),
   list: os
     .input(messageQuerySchema)
     .handler(({ input }) => messagesService.listMessages(input)),