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/components/soundboard-pack-view/UserSoundboardPack.tsx

@@ -0,0 +1,32 @@
+import React, { useCallback, useMemo } from 'react';
+import { SoundboardPackEditor } from './SoundboardPackEditor';
+import { SoundboardContent, SoundboardPack } from '../../plugins/soundboard';
+import { useMatrixClient } from '../../hooks/useMatrixClient';
+import { AccountDataEvent } from '../../../types/matrix/accountData';
+import { useUserSoundboardPack } from '../../hooks/useSoundboardPacks';
+
+export function UserSoundboardPack() {
+  const mx = useMatrixClient();
+  const defaultPack = useMemo(
+    () =>
+      new SoundboardPack(
+        mx.getUserId() ?? '',
+        { pack: { display_name: 'My Soundboard' } },
+        undefined,
+      ),
+    [mx],
+  );
+  const pack = useUserSoundboardPack() ?? defaultPack;
+
+  const handleUpdate = useCallback(
+    async (content: SoundboardContent) => {
+      await mx.setAccountData(
+        AccountDataEvent.LotusSoundboard as unknown as keyof import('matrix-js-sdk').AccountDataEvents,
+        content as never,
+      );
+    },
+    [mx],
+  );
+
+  return <SoundboardPackEditor pack={pack} canEdit onUpdate={handleUpdate} />;
+}