v5.5.0
Marketing config keys renamed from platform-specific to role-based:
marketing.sendgrid→marketing.campaigns(withplatform: 'sendgrid')marketing.beehiiv→marketing.newsletter(withplatform: 'beehiiv')
This decouples the config shape from the underlying provider, so swapping platforms only requires changing the platform property instead of restructuring the config.
NeverBounce mailbox verification added as the preferred provider (NEVERBOUNCE_API_KEY), with ZeroBounce kept as fallback. Provider logic extracted into pluggable modules.
Breaking: All consumer backend-manager-config.json files must rename sendgrid → campaigns and beehiiv → newsletter under marketing:, adding the platform property.