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/plugins/soundboard/SoundboardMetaReader.ts

@@ -0,0 +1,29 @@
+import { SoundboardMeta } from './types';
+
+/** Parallels custom-emoji/PackMetaReader (no usage tiers for soundboard). */
+export class SoundboardMetaReader {
+  private readonly meta: SoundboardMeta;
+
+  constructor(meta: SoundboardMeta) {
+    this.meta = meta;
+  }
+
+  get name(): string | undefined {
+    const displayName = this.meta.display_name;
+    return typeof displayName === 'string' ? displayName : undefined;
+  }
+
+  get avatar(): string | undefined {
+    const avatarURL = this.meta.avatar_url;
+    return typeof avatarURL === 'string' ? avatarURL : undefined;
+  }
+
+  get attribution(): string | undefined {
+    const { attribution } = this.meta;
+    return typeof attribution === 'string' ? attribution : undefined;
+  }
+
+  get content(): SoundboardMeta {
+    return this.meta;
+  }
+}