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/features/room/RoomInput.tsx

@@ -26,6 +26,7 @@ import {
   Scroll,
   Spinner,
   Text,
+  color,
   config,
   toRem,
 } from 'folds';
@@ -122,6 +123,7 @@ import { usePowerLevelTags } from '../../hooks/usePowerLevelTags';
 import { useComposingCheck } from '../../hooks/useComposingCheck';
 import { VoiceMessageRecorder } from '../../components/VoiceMessageRecorder';
 import { PollCreator } from './PollCreator';
+import { useRoomUnverifiedDeviceCount } from '../../hooks/useDeviceVerificationStatus';
 
 const GifPicker = React.lazy(() =>
   import('../../components/GifPicker').then((m) => ({ default: m.GifPicker })),
@@ -144,6 +146,15 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
     const [isMarkdown] = useSetting(settingsAtom, 'isMarkdown');
     const [hideActivity] = useSetting(settingsAtom, 'hideActivity');
     const [legacyUsernameColor] = useSetting(settingsAtom, 'legacyUsernameColor');
+    const [warnOnUnverifiedDevices] = useSetting(settingsAtom, 'warnOnUnverifiedDevices');
+    const crypto = mx.getCrypto();
+    const roomUnverifiedDeviceCount = useRoomUnverifiedDeviceCount(crypto, room);
+    const isEncrypted = room.hasEncryptionStateEvent();
+    const showUnverifiedWarning =
+      warnOnUnverifiedDevices &&
+      isEncrypted &&
+      roomUnverifiedDeviceCount !== undefined &&
+      roomUnverifiedDeviceCount > 0;
     const direct = useIsDirectRoom();
     const commands = useCommands(mx, room);
     const emojiBtnRef = useRef<HTMLButtonElement>(null);
@@ -718,6 +729,27 @@ export const RoomInput = forwardRef<HTMLDivElement, RoomInputProps>(
             requestClose={handleCloseAutocomplete}
           />
         )}
+        {showUnverifiedWarning && (
+          <Box
+            alignItems="Center"
+            gap="200"
+            style={{
+              padding: `${config.space.S100} ${config.space.S300}`,
+              background: color.Warning.Container,
+            }}
+          >
+            <Icon
+              size="100"
+              src={Icons.Shield}
+              style={{ color: color.Warning.OnContainer, flexShrink: 0 }}
+            />
+            <Text size="T200" style={{ color: color.Warning.OnContainer }}>
+              {roomUnverifiedDeviceCount}{' '}
+              {roomUnverifiedDeviceCount === 1 ? 'unverified device' : 'unverified devices'} in this
+              room
+            </Text>
+          </Box>
+        )}
         <CustomEditor
           editableName="RoomInput"
           editor={editor}