feat: ship ad-supported only — gate Remove Ads IAP behind kIapEnabled=false

The developer is an individual without a Korean business registration, so
the App Store / Play paid-apps (merchant) agreements can't be completed.
Hide the Remove Ads + Restore tiles and skip IAP init; ads always show.
AdMob revenue is independent of those agreements. Reversible: flip
kIapEnabled to re-enable once a merchant agreement exists. Bump to build 2;
drop the now-unused IAP review-screenshot generator.

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

docs/zardu_closed_testers_list_20251225.csv

@@ -0,0 +1,28 @@
+zardu.plum@gmail.com
+zardu.sqa.101@gmail.com
+zardu.sqa.102@gmail.com
+zardu.sqa.103@gmail.com
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+zardu.sqa.107@gmail.com
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+zardu.sqa.121@gmail.com
+axiom.kor@gmail.com
+boson.seoul@gmail.com
+cepheid.space@gmail.com
+diffraction.rayman@gmail.com
+duality.frame@gmail.com
+quantum.tteokshop@gmail.com