fix(mobile): useModalStyle on 3 more dialogs, GPU hint animated bg, document untested fixes

- DeviceVerification, InviteUserPrompt, LogoutDialog: apply useModalStyle for
  fullscreen on mobile, capped box on desktop
- chatBackground: inject willChange + contain:paint on animated variants to
  promote compositor layer and prevent descendant repaint flickering (Bug #2)
- LOTUS_BUGS.md: mark #7-#10 FIXED/UNTESTED, #2 FIXED/UNTESTED, chatBackground
  backgroundColor values as PATTERN CONTENT EXCEPTION

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

src/app/components/invite-user-prompt/InviteUserPrompt.tsx

@@ -51,6 +51,7 @@ import { useAlive } from '../../hooks/useAlive';
 import { copyToClipboard } from '../../utils/dom';
 import { getMatrixToRoom } from '../../plugins/matrix-to';
 import { getViaServers } from '../../plugins/via-servers';
+import { useModalStyle } from '../../hooks/useModalStyle';
 
 const SEARCH_OPTIONS: UseAsyncSearchOptions = {
   limit: 1000,
@@ -66,6 +67,7 @@ type InviteUserProps = {
 };
 export function InviteUserPrompt({ room, requestClose }: InviteUserProps) {
   const mx = useMatrixClient();
+  const modalStyle = useModalStyle(560);
   const alive = useAlive();
   const [linkCopied, setLinkCopied] = useState(false);
   const [showQr, setShowQr] = useState(false);
@@ -184,7 +186,7 @@ export function InviteUserPrompt({ room, requestClose }: InviteUserProps) {
             escapeDeactivates: stopPropagation,
           }}
         >
-          <Dialog>
+          <Dialog style={modalStyle}>
             <Box grow="Yes" direction="Column">
               <Header
                 size="500"