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/components/CallEmbedProvider.tsx

@@ -45,6 +45,7 @@ import { useMatrixClient } from '../hooks/useMatrixClient';
 import { previewRingtone, startRingtone } from '../utils/ringtones';
 import { useCallMembersChange, useCallSession } from '../hooks/useCall';
 import { useCallJoinLeaveSounds } from '../hooks/useCallJoinLeaveSounds';
+import { useCallQuality } from '../hooks/useCallQuality';
 import { useRemoteAllMuted } from '../hooks/useCallSpeakers';
 import { useRoomAvatar, useRoomName } from '../hooks/useRoomMeta';
 import { mDirectAtom } from '../state/mDirectList';
@@ -584,6 +585,7 @@ function CallUtils({ embed }: { embed: CallEmbed }) {
   useCallMemberSoundSync(embed);
   useCallJoinLeaveSounds(embed);
   useCallThemeSync(embed);
+  useCallQuality(embed);
   useCallHangupEvent(
     embed,
     useCallback(() => {