Add a pre-seeded demo tile to the scan hero

[slavazeph-coder]

brainsnn-r3f-app/src/components/DemoTiles.jsx

Add an extra tile (e.g. AI-generated political ad, viral product launch, scam DM, grief-bait headline) to the TILES array with a short example text + emoji + hint label.

The existing six tiles (Outrage headline, Fear cascade, Urgency ad copy, Trust attack email, Calm rewrite, Public perception risk) show the pattern — each is a real piece of manipulative (or calm) writing that lights up different firewall dimensions when scanned.