Fix duplicate text on invitation page header

- Removed redundant "Invite to {group name}" text
- Now shows only group avatar, private chip, and personalized invite heading
- Eliminates duplication like "Invite to Anyville Community Garden" + "Invite Sarah Johnson to Anyville Community Garden"

🤖 Generated with [Claude Code](https://claude.ai/code)

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

src/pages/InvitationPage.tsx

@@ -242,9 +242,6 @@ const InvitationPage = () => {
               <Groups />
             </Avatar>
             <Box>
-              <Typography variant="h4" component="h1" gutterBottom>
-                Invite to {group.name}
-              </Typography>
               {group.isPrivate && (
                 <Chip label="Private Group" size="small" variant="outlined" />
               )}