Add CTO takeover: full-page flip + gradient banner

[luaroncrew]

Summary

• Flips the entire page 180° via transform: rotate(180deg) on html.flipped (set on page load)
• Adds a position: fixed banner counter-rotated 180° so it reads correctly at the top of the viewport
• Banner text: "Your CTO has arrived. The old ways are over."
• Bold gradient background: purple (#7b2ff7) → pink (#f107a3) → orange (#ff6a00)
• Restore Order button removes the flipped class and hides the banner — pure CSS transforms, zero JS animation libraries
• Applied to both frontend/index.html and frontend-v3/index.html

Test plan

• Open either frontend — page should appear upside-down on load
• Banner should be readable at the top with gradient background
• Click "Restore Order" — page flips right-side up, banner disappears
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