Fix Android media downloads and dismiss notifs when read elsewhere.

FileSaver fails in Capacitor WebView, so save via MediaStore; clear tray notifications when sync reports rooms as read on another device, and improve collapsed notification avatars with conversation shortcuts.

overlay/src/app/components/video-viewer/VideoViewer.tsx

@@ -0,0 +1,74 @@
+import React from 'react';
+import classNames from 'classnames';
+import { Box, Chip, Header, IconButton, Text, as } from 'folds';
+import { Icon, Icons } from '../icons';
+import * as css from './VideoViewer.css';
+import { downloadAndSaveMedia } from '../../utils/saveMedia';
+import { getCurrentAccessToken } from '../../utils/auth';
+
+export type VideoViewerProps = {
+  alt: string;
+  src: string;
+  requestClose: () => void;
+};
+
+export const VideoViewer = as<'div', VideoViewerProps>(
+  ({ className, alt, src, requestClose, ...props }, ref) => {
+    const handleDownload = async () => {
+      try {
+        await downloadAndSaveMedia(src, alt, getCurrentAccessToken());
+      } catch (error) {
+        console.warn('[VideoViewer] Failed to download media:', error);
+        try {
+          window.open(src, '_blank');
+        } catch {
+          // ignore
+        }
+      }
+    };
+
+    return (
+      <Box
+        className={classNames(css.VideoViewer, className)}
+        direction="Column"
+        {...props}
+        ref={ref}
+      >
+        <Header className={css.VideoViewerHeader} size="400">
+          <Box grow="Yes" alignItems="Center" gap="200">
+            <IconButton size="300" radii="300" onClick={requestClose}>
+              <Icon size="50" src={Icons.ArrowLeft} />
+            </IconButton>
+            <Text size="T300" truncate>
+              {alt}
+            </Text>
+          </Box>
+          <Box shrink="No" alignItems="Center" gap="200">
+            <Chip
+              variant="Primary"
+              onClick={handleDownload}
+              radii="300"
+              before={<Icon size="50" src={Icons.Download} />}
+            >
+              <Text size="B300">Download</Text>
+            </Chip>
+          </Box>
+        </Header>
+        <Box
+          grow="Yes"
+          className={css.VideoViewerContent}
+          justifyContent="Center"
+          alignItems="Center"
+        >
+          <video
+            className={css.VideoViewerVideo}
+            src={src}
+            title={alt}
+            controls
+            autoPlay
+          />
+        </Box>
+      </Box>
+    );
+  }
+);