Attribution window is configurable, not hard-coded

Attribution windows determine how far back from a conversion you look for a causal email touchpoint. A 7-day window and a 30-day window produce materially different revenue attribution numbers for the same campaign — especially for products with long consideration cycles. If the window is a magic number hard-coded in four different query files, changing your attribution model to match your actual sales cycle requires a multi-file search-and-replace with no guarantee you caught every instance. This is an iso-25010:2011 maintainability failure: the system cannot adapt to a known parameter without engineering effort and regression risk.

Extract the attribution window to a single named constant sourced from an environment variable so it can be changed in one place without touching query logic:

// lib/attribution/config.ts
export const ATTRIBUTION_WINDOW_DAYS = parseInt(
  process.env.ATTRIBUTION_WINDOW_DAYS ?? '30',
  10
)

export function getAttributionWindowStart(): Date {
  return new Date(Date.now() - ATTRIBUTION_WINDOW_DAYS * 24 * 60 * 60 * 1000)
}

Import getAttributionWindowStart() in every attribution query. Set ATTRIBUTION_WINDOW_DAYS in your environment config (.env.local, Vercel env vars) so it's tunable without a deploy. Document the chosen value and rationale in a comment near the constant.