Dry-run only: returns each account's current vs proposed Tier 1/2/3 bucket with its score, plus the plan
caps and how many slots are used, the per-tier refresh cadence, and whether tiering is enabled. Persists
nothing. The affiliate is taken from the request context (the x-affiliate-id scope).

🔐 Required permission: AccountAdmin

🔐 Requires an Affiliate context (AffiliateId in header or token)