Wall ownership ladder: positions 2 and 3 become the member's own at 2 / 5 qualifying buyers

- accounts.wall_offers (JSON, up to 2 offers: label, https link, banner) set from
  Profile > Your wall; upload supported; locks show the buyer threshold.
- /api/wall assembles: position 1 = own line banner; positions 2-3 = own offer
  when unlocked and set, else upline banners (only uplines with a live banner),
  else house ads. Response carries unlocked + buyerCount; wall labels show
  "this wall" / "their line" / "InstantAdPay".
- Chatbot canned answer + facts, follow-up email 7 mention the ladder.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

db.js

@@ -185,6 +185,7 @@ async function bootstrap() {
     INDEX (stopped, next_at)
   ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4`);
   await alterSafe('ALTER TABLE accounts ADD COLUMN joined_via VARCHAR(20) NULL'); // ?v= angle the lead came in on
+  await alterSafe('ALTER TABLE accounts ADD COLUMN wall_offers VARCHAR(2000) NULL'); // JSON [{title,bannerUrl,targetUrl}] for wall positions 2-3 (unlock at 2 / 5 qualifying buyers)
 }
 
 // one-time import: only when the tables are empty and JSON files exist