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/SoundboardClipReader.ts

@@ -0,0 +1,58 @@
+import { SoundboardClip, SoundboardClipInfo } from './types';
+
+/** Parallels custom-emoji/PackImageReader, for a soundboard clip. */
+export class SoundboardClipReader {
+  public readonly shortcode: string;
+
+  public readonly url: string;
+
+  private readonly clip: Omit<SoundboardClip, 'url'>;
+
+  constructor(shortcode: string, url: string, clip: Omit<SoundboardClip, 'url'>) {
+    this.shortcode = shortcode;
+    this.url = url;
+    this.clip = clip;
+  }
+
+  static fromClip(shortcode: string, clip: SoundboardClip): SoundboardClipReader | undefined {
+    const { url } = clip;
+    if (typeof url !== 'string' || !url.startsWith('mxc://')) return undefined;
+    return new SoundboardClipReader(shortcode, url, clip);
+  }
+
+  get body(): string | undefined {
+    const { body } = this.clip;
+    return typeof body === 'string' ? body : undefined;
+  }
+
+  /** Display name — the clip body, falling back to the shortcode. */
+  get name(): string {
+    return this.body ?? this.shortcode;
+  }
+
+  get emoji(): string | undefined {
+    const { emoji } = this.clip;
+    return typeof emoji === 'string' && emoji.length > 0 ? emoji : undefined;
+  }
+
+  /** Per-clip volume 0–100; defaults to 100 when unset/invalid. */
+  get volume(): number {
+    const v = this.clip.volume;
+    if (typeof v !== 'number' || Number.isNaN(v)) return 100;
+    return Math.min(100, Math.max(0, v));
+  }
+
+  get info(): SoundboardClipInfo | undefined {
+    return this.clip.info;
+  }
+
+  get content(): SoundboardClip {
+    return {
+      url: this.url,
+      body: this.clip.body,
+      emoji: this.clip.emoji,
+      volume: this.clip.volume,
+      info: this.clip.info,
+    };
+  }
+}