chore: merge v4.12.1 — security, calling, editor, media fixes

Key v4.12.1 changes merged:
- Security: sanitize-html updated to v2.17.4
- Calling: video calls in DMs/rooms, user avatars during calls, right-click to start
- Calling: IncomingCallListener with ring sound and answer/reject UI
- Editor: list crash fixes (Firefox + empty headings), codeblock filename support
- Media: URL preview hover state, keyboard nav, click-to-open, OGG audio support
- Date: ISO 8601 (YYYY-MM-DD) date format option
- Misc: stable mutual rooms endpoint, Android notification crash fix

Lotus customisations preserved:
- PiP drag/resize, DM call ring notification, PTT, GIF picker, noise suppression
- Poll voting, message forwarding, image captions, location sharing
- Lotus Terminal design theme

src/app/pages/client/SpecVersions.tsx

@@ -22,7 +22,7 @@ export function SpecVersions({ baseUrl, children }: { baseUrl: string; children:
             <Dialog>
               <Box direction="Column" gap="400" style={{ padding: config.space.S400 }}>
                 <Text>
-                  Failed to connect to homeserver. Either homeserver is down or your internet.
+                  Unable to connect to the homeserver. The homeserver or your internet connection may be down.
                 </Text>
                 <Button variant="Critical" onClick={retry}>
                   <Text as="span" size="B400">