Instagram Follower Growth

Reports how many Instagram FOLLOWERS an account gained per day, so follower/profile-visit campaigns can finally be measured. Meta's insights `actions` breakdown has NO follower row for OUTCOME_TRAFFIC/PROFILE_VISIT campaigns (only link_click, video_view, post_engagement), and the true follower_count metric lives behind Instagram Insights permissions this app does not hold. So we snapshot followers_count daily (it IS available with ads_management) and diff it. Returns per Instagram account: series [{day, followers, delta}], first, last, gained, days_tracked — plus today's live count. History starts the first day tracking ran; Meta exposes no historical follower numbers, so a daily change needs at least two days of data. Combine `gained` with the campaign's spend from meta_campaign_insights for a cost-per-follower estimate; state clearly that this is account-level growth, not click-attributed.