feat(call): in-call soundboard, quality controls, room call-permissions

Element Call is now consumed as our self-built fork
(@lotusguild/element-call-embedded); wire up its previously-dormant
capabilities and document the fork as live.

Soundboard (P5-15): a call-bar button plays user-uploaded audio clips into the
call as a real published track (io.lotus.inject_audio) plus local playback.
Clips are uploadable like emoji/sticker packs, stored in io.lotus.soundboard
account data (synced across devices). Gated by a Settings toggle + volume.

Quality controls (P5-31): per-user mic/screenshare bitrate + screenshare
framerate (Settings -> Calls), applied via io.lotus.set_quality clamped to any
room cap. Room admins set caps and hard call-permissions (allow_screenshare /
allow_camera) in Room Settings -> Voice; the call bar hides blocked buttons.

- New: CallSoundboard, useSoundboard, soundboardClips; RoomQuality,
  useCallQuality, callQuality (+ unit tests).
- Optimistic-write RoomQuality admin UI (no stale-state clobber).
- Docs: mark EC fork live across README/FEATURES/TODO/BUGS/TESTING; add D2
  manual-test steps.

Numeric quality caps are client-cooperative; screenshare/camera permissions are
hard-enforced server-side (see LotusGuild/matrix voice-limit-guard).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/state/settings.ts

@@ -24,6 +24,13 @@ export type DenoiseModelId = 'rnnoise' | 'speex' | 'dtln' | 'deepfilternet';
 // 'soft' / 'retro' are synthesized in-browser (see utils/ringtones.ts);
 // 'none' is silent (visual-only incoming-call UI).
 export type RingtoneId = 'classic' | 'chime' | 'soft' | 'retro' | 'none';
+// [P5-31] Granular call quality caps. 'auto' = don't cap (the EC fork keeps its
+// default encoding). Numbers are kbps (audio/screenshare bitrate) or fps
+// (screenshare framerate); converted to the fork's bits/sec + fps payload in
+// utils/callQuality.ts and applied via the io.lotus.set_quality widget action.
+export type CallAudioBitrate = 'auto' | '32' | '64' | '96' | '128' | '256';
+export type ScreenshareBitrate = 'auto' | '500' | '1500' | '3000' | '8000';
+export type ScreenshareFramerate = 'auto' | '15' | '30' | '60';
 export type ChatBackground =
   | 'none'
   | 'blueprint'
@@ -156,6 +163,14 @@ export interface Settings {
   ringtoneId: RingtoneId;
   ringtoneVolume: number; // 0–100
 
+  // [P5-31] Call quality controls
+  callAudioBitrate: CallAudioBitrate;
+  screenshareBitrate: ScreenshareBitrate;
+  screenshareFramerate: ScreenshareFramerate;
+  // [P5-15] In-call soundboard
+  soundboardEnabled: boolean;
+  soundboardVolume: number; // 0–100
+
   seasonalThemeOverride:
     | 'auto'
     | 'off'
@@ -253,6 +268,12 @@ const defaultSettings: Settings = {
   ringtoneId: 'classic',
   ringtoneVolume: 70,
 
+  callAudioBitrate: 'auto',
+  screenshareBitrate: 'auto',
+  screenshareFramerate: 'auto',
+  soundboardEnabled: true,
+  soundboardVolume: 80,
+
   seasonalThemeOverride: 'auto',
 };