Upgrade Sponsored Brands v3 to v4, Boost ROAS

Migrate Amazon Sponsored Brands from v3 to v4 now. v3 APIs were deprecated Jan 31, 2024; remaining legacy campaigns face feature lockout, data gaps in newer reporting, and occasional rejections. Benefits of v4: multi-ad group campaigns, editable creatives without resetting history, and compatible reporting endpoints. Practical plan: 1) audit legacy campaigns (esp. pre-2023), 2) clone to v4, 3) segment ad groups by brand, category, competitor, and product targeting, 4) rebuild negatives and bids, 5) refresh creatives in place, 6) switch to the latest Amazon Ads API endpoints, 7) run a 7–14 day overlap test to validate parity, then sunset v3.