Agency_Portal_Email_Settings - Registers settings, renders form fields, manages configuration Agency_Portal_Email_Relay_Compositor - Receives webhook triggers, composes email with placeholders, dispatches Agency_Portal_Email_Scheduler - Orchestrates mission creation on external server when invoice created/modified Settings page uses standard WordPress settings API: Settings registered via register_setting() Fields rendered via add_settings_field() Email body uses wp_editor() WYSIWYG editor Time selector uses dual dropdowns for hour and minute Reminder rules use dynamic JS to add/remove inputs Hook Type Purpose apapi_invoice_display_total Filter Format amount for Multi-Currency plugin agency_pulse_email_relay_trigger Action Receive webhook trigger from external server