Rebrand the auth screen for the RPG experience

[aphexlog]

Summary

• Reworked the login screen copy to present Brain in Cup as a conventional fantasy RPG app, not a consciousness experiment
• Updated the hero messaging, supporting bullets, and call-to-action language to focus on character creation, quests, dice, inventory, and campaign history
• Aligned page and manifest metadata with the new RPG positioning and removed explicit AI framing from the auth surface

Testing

• npm run build passed
• Verified the updated branding text in the auth component and metadata files