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/features/call/CallControls.tsx

@@ -351,10 +351,6 @@ export function CallControls({ callEmbed }: CallControlsProps) {
           <Box shrink="No" alignItems="Inherit" justifyContent="Inherit" gap="200">
             <MicrophoneButton enabled={microphone} onToggle={handleMicrophoneToggle} />
             <SoundButton enabled={sound} onToggle={() => callEmbed.control.toggleSound()} />
-            <ScreenshareAudioButton
-              muted={screenshareAudioMuted}
-              onToggle={() => callEmbed.control.toggleScreenshareAudio()}
-            />
           </Box>
           {!compact && showVideoGroup && <ControlDivider />}
           {showVideoGroup && (
@@ -363,12 +359,20 @@ export function CallControls({ callEmbed }: CallControlsProps) {
                   user can stop it; once stopped it hides and can't be restarted. */}
               {showCamera && <VideoButton enabled={video} onToggle={handleVideoToggle} />}
               {showScreenshare && (
-                <ScreenShareButton
-                  enabled={screenshare}
-                  onToggle={() =>
-                    screenshare ? callEmbed.control.toggleScreenshare() : setShareConfirm(true)
-                  }
-                />
+                <>
+                  <ScreenShareButton
+                    enabled={screenshare}
+                    onToggle={() =>
+                      screenshare ? callEmbed.control.toggleScreenshare() : setShareConfirm(true)
+                    }
+                  />
+                  {/* Mute-screenshare-audio sits directly next to the screenshare
+                      control since they're the same concern. */}
+                  <ScreenshareAudioButton
+                    muted={screenshareAudioMuted}
+                    onToggle={() => callEmbed.control.toggleScreenshareAudio()}
+                  />
+                </>
               )}
               {!!document.fullscreenEnabled && (
                 <FullscreenButton isFullscreen={isFullscreen} onToggle={handleFullscreen} />