feat: PiP mute indicator, export history, activity log, unverified device warning

- PiP call window: mute overlay using MutationObserver on EC iframe's
  [data-testid="incall_mute"] button (data-kind="primary" = muted),
  same pattern as screenshare detection in CallControl.ts

- P2-4 Export Room History: new tab in room settings — Plain Text / JSON /
  HTML formats, optional date range, progress counter, paginated via
  paginateEventTimeline, blob download; E2EE-aware (skips failed decryptions)

- P2-6 Room Activity Log: new tab in room settings — filterable log of
  m.room.member, m.room.power_levels, m.room.name/topic/avatar/server_acl
  events with human-readable descriptions, relative timestamps, Load More
  pagination

- P2-10 Unverified Device Warning: warnOnUnverifiedDevices setting (default
  off); Warning.Container banner above composer in encrypted rooms with
  unverified devices; toggle in Settings → General → Privacy

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/components/CallEmbedProvider.tsx

@@ -41,6 +41,7 @@ import { ScreenSize, useScreenSizeContext } from '../hooks/useScreenSize';
 import { useMatrixClient } from '../hooks/useMatrixClient';
 import CallSound from '../../../public/sound/call.ogg';
 import { useCallMembersChange, useCallSession } from '../hooks/useCall';
+import { useRemoteAllMuted } from '../hooks/useCallSpeakers';
 import { useRoomAvatar, useRoomName } from '../hooks/useRoomMeta';
 import { mDirectAtom } from '../state/mDirectList';
 import { useMediaAuthentication } from '../hooks/useMediaAuthentication';
@@ -402,6 +403,37 @@ function CallUtils({ embed }: { embed: CallEmbed }) {
   return null;
 }
 
+/** Shown inside the PiP window when the local microphone is muted. */
+function PipMuteOverlay({ callEmbed }: { callEmbed: CallEmbed }) {
+  const allMuted = useRemoteAllMuted(callEmbed);
+  if (!allMuted) return null;
+  return (
+    <div
+      aria-label="Microphone muted"
+      style={{
+        position: 'absolute',
+        bottom: '8px',
+        left: '8px',
+        zIndex: 3,
+        background: 'rgba(0,0,0,0.60)',
+        backdropFilter: 'blur(4px)',
+        borderRadius: '6px',
+        padding: '3px 7px',
+        display: 'flex',
+        alignItems: 'center',
+        gap: '4px',
+        pointerEvents: 'none',
+        color: color.Critical.Main,
+        fontSize: '13px',
+        lineHeight: 1,
+        userSelect: 'none',
+      }}
+    >
+      <Icon size="100" src={Icons.MicMute} filled />
+    </div>
+  );
+}
+
 type CallEmbedProviderProps = {
   children?: ReactNode;
 };
@@ -803,6 +835,7 @@ export function CallEmbedProvider({ children }: CallEmbedProviderProps) {
                 ↗ Return to call
               </div>
             </div>
+            <PipMuteOverlay callEmbed={callEmbed} />
             {(['se', 'sw', 'ne', 'nw'] as Corner[]).map((corner) => {
               const s = corner.includes('s');
               const e2 = corner.includes('e');