v1.0.0 of influto

Track influencer referrals, attribution, and store-direct purchase validation in your Flutter app. Mirrors the InfluTo React Native SDK. Changelog excerpt: Initial release of the InfluTo Flutter SDK. ### Added - Full influencer attribution API: initialize, checkAttribution, identifyUser, trackEvent, getActiveCampaigns, validateCode, setReferralCode, applyCode, getReferralCode, getPrefilledCode, clearAttribution— matching the canonical cross-platform contract (wire 1.0.0). - Store-direct purchase validation via reportPurchase(StoreKit 2 JWS on iOS, Play purchase token on Android), posting to /sdk/purchase. Supports one-ti[...]