If someone with a private profile gets visited by a non-friend (or a guest), the old behavior was echo "This profile is private." + exit — no site chrome, no way back, just a wall of plain text.
Now renders a full site-layout page with:
- A centered card carrying a lock icon, the reason, and two fallback links (Who's Online, Back to Forums)
- An auto-opening modal overlay that explains the situation and gives contextual guidance (friends-only profiles tell guests to log in and send a friend request; members get told to send a friend request)
- Still HTTP 403 underneath, so crawlers and API clients see this as a block rather than a content page
Covers both privacy tiers: private and friends_only.
