Buy flow: survive mobile app-switch fetch drops

Mobile drops in-flight fetches when the page returns from the wallet app, which
aborted the purchase before the tx ("Failed to fetch"). Retry /api/me and
/api/sponsor, and make waitTx keep polling through transient fetch failures.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

public/assets/my.js

@@ -1223,12 +1223,15 @@
           // the buyer's credits are read by the member id of their LINKED wallet.
           // If they only connected a wallet (e.g. for the faucet) but never linked
           // it, link it first (one signature) so the purchase's credits show up.
-          const meNow = await (await fetch('/api/me')).json();
+          // retry these through transient failures — mobile drops in-flight
+          // fetches when the page returns from the wallet app-switch
+          const jretry = async url => { let err; for (let i = 0; i < 4; i++) { try { return await (await fetch(url)).json(); } catch (e) { err = e; await new Promise(s => setTimeout(s, 500 * (i + 1))); } } throw err; };
+          const meNow = await jretry('/api/me');
           if (!meNow.address) {
             IAP.status('Link your wallet first — one quick signature…');
             await IAPWallet.signIn();
           }
-          const spNow = await (await fetch('/api/sponsor')).json();
+          const spNow = await jretry('/api/sponsor');
           IAP.status('Confirm the purchase in your wallet…');
           const r = await IAPWallet.buy(Number(b.dataset.id), spNow.sponsorId || 0, b.dataset.cost);
           if (r.status !== '0x1' && r.receipt && r.receipt.status !== '0x1') throw new Error('Transaction reverted.');