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/hooks/useDeviceVerificationStatus.ts

@@ -1,4 +1,5 @@
-import { useCallback, useEffect, useState } from 'react';
+import { useCallback, useEffect, useMemo, useState } from 'react';
+import { Room } from 'matrix-js-sdk';
 import { CryptoApi } from 'matrix-js-sdk/lib/crypto-api';
 import { verifiedDevice } from '../utils/matrix-crypto';
 import { useAlive } from './useAlive';
@@ -104,3 +105,62 @@ export const useUnverifiedDeviceCount = (
 
   return unverifiedCount;
 };
+
+export const useRoomUnverifiedDeviceCount = (
+  crypto: CryptoApi | undefined,
+  room: Room,
+): number | undefined => {
+  const [unverifiedCount, setUnverifiedCount] = useState<number>();
+  const alive = useAlive();
+
+  const memberIds = useMemo(
+    () => room.getJoinedMembers().map((m) => m.userId),
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+    [room.roomId],
+  );
+
+  const updateCount = useCallback(async () => {
+    if (!crypto) return;
+
+    const deviceMap = await crypto.getUserDeviceInfo(memberIds);
+    let count = 0;
+
+    const allChecks: Promise<boolean | null>[] = [];
+
+    deviceMap.forEach((devices, userId) => {
+      devices.forEach((_device, deviceId) => {
+        allChecks.push(verifiedDevice(crypto, userId, deviceId));
+      });
+    });
+
+    const results = await Promise.allSettled(allChecks);
+    const settled = fulfilledPromiseSettledResult(results);
+    settled.forEach((status) => {
+      if (status === false) {
+        count += 1;
+      }
+    });
+
+    if (alive()) {
+      setUnverifiedCount(count);
+    }
+  }, [crypto, memberIds, alive]);
+
+  useDeviceListChange(
+    useCallback(
+      (userIds) => {
+        const affected = userIds.some((uid) => memberIds.includes(uid));
+        if (affected) {
+          updateCount();
+        }
+      },
+      [memberIds, updateCount],
+    ),
+  );
+
+  useEffect(() => {
+    updateCount();
+  }, [updateCount]);
+
+  return unverifiedCount;
+};