feat(soundboard): shared room/space packs (like emoji/stickers), grid picker, management

Soundboard v2 — a near-parallel of the custom-emoji image-pack system for
in-call audio clips.

- Data model: 3-tier packs mirroring MSC2545 — room/space pack (state event
  io.lotus.soundboard, inherited by child rooms via parent-space aggregation),
  global refs (io.lotus.soundboard_rooms), and the personal pack
  (io.lotus.soundboard account data; the v1 flat-list content is migrated to the
  pack shape on read). New plugins/soundboard/ (readers, SoundboardPack, utils) +
  hooks/useSoundboardPacks (useRelevantSoundboardPacks = user U global U room,
  deduped). Unit-tested (migration + slug).
- Management: reusable SoundboardPackEditor (name + emoji + per-clip volume +
  delete + upload + batched save), power-level-gated for room packs like emoji
  packs; a Soundboard page wired into Room + Space settings.
- In-call: CallSoundboard rewritten as a Discord-style grid grouped by pack
  (emoji + name tiles), sourcing room+parent-space U personal clips; a Manage
  toggle embeds the editors; per-clip volume x master volume on playback.
- Spam guard: host gates on a playing key (fork enforces one clip at a time).
- Control bar: Mute-Screenshare moved next to the Screenshare button.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/app/features/room-settings/RoomSettings.tsx

@@ -13,6 +13,7 @@ import { RoomAvatar, RoomIcon } from '../../components/room-avatar';
 import { General } from './general';
 import { Members } from '../common-settings/members';
 import { EmojisStickers } from '../common-settings/emojis-stickers';
+import { Soundboard } from '../common-settings/soundboard';
 import { Permissions } from './permissions';
 import { RoomSettingsPage } from '../../state/roomSettings';
 import { useRoom } from '../../hooks/useRoom';
@@ -53,6 +54,11 @@ const BASE_MENU_ITEMS: RoomSettingsMenuItem[] = [
     name: 'Emojis & Stickers',
     icon: Icons.Smile,
   },
+  {
+    page: RoomSettingsPage.SoundboardPage,
+    name: 'Soundboard',
+    icon: Icons.Bell,
+  },
   {
     page: RoomSettingsPage.DeveloperToolsPage,
     name: 'Developer Tools',
@@ -226,6 +232,9 @@ export function RoomSettings({ initialPage, requestClose }: RoomSettingsProps) {
       {activePage === RoomSettingsPage.EmojisStickersPage && (
         <EmojisStickers requestClose={handlePageRequestClose} />
       )}
+      {activePage === RoomSettingsPage.SoundboardPage && (
+        <Soundboard requestClose={handlePageRequestClose} />
+      )}
       {activePage === RoomSettingsPage.DeveloperToolsPage && (
         <DeveloperTools requestClose={handlePageRequestClose} />
       )}