Restrict access to authenticated-only features

[MasterGordon]

I have implemented several changes to ensure that parts of the application intended for logged-in users are properly restricted and provide clear "Call to Action" (CTA) points for guests.

Key changes:

1. Route Protection: Created a ProtectedRoute component in src/main.tsx that gates access to /history, /settings, and /collection. Guests are now met with a friendly login message and CTA.
2. Dynamic UI Visibility: Updated the sidebar in Shell.tsx to use the authenticated username from the server to determine which navigation links to show, replacing the less reliable local token check.
3. Context-Specific CTAs:
   • The Store now displays a "Login to Buy" button for guests instead of a simple "Buy" button that would fail.
   • The Play page now shows a "Sign in to Play" button for guests.
   • Updated RegisterButton to accept a label prop for these custom CTAs.
4. Session Integrity: Modified the startup logic in src/main.tsx to automatically remove the loginToken from localStorage if it's found to be invalid or expired during initial connection.
5. Code Cleanup: Removed unused variables and imports identified during type checking.

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PR created automatically by Jules for task 2097218213544781789 started by @MasterGordon

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