Profile Dropdown Polish

• Icons on every menu item. The profile dropdown in the app bar now shows a small icon next to each option — Profile, My Claims, My Sources, Settings, Logout, Report Issue, Debug Mode, and Login — making the menu easier to scan at a glance.

Better Link Previews

• Open Graph and Twitter card metadata. Argument view pages now include richer metadata so that when someone shares a Proposit argument on social media or in chat apps, the preview shows the argument's actual title, description, and Proposit branding instead of a generic fallback.
• Argument title in the browser tab. The page title now leads with the argument's own title (e.g. "My Argument — Proposit") rather than a generic "Proposit: ..." prefix.
• Untitled argument fallback. Arguments saved without a title now display as "Untitled Argument" in tabs and link previews instead of an empty string.