PhoenixKit V05 Migration: Add Beneficiary Field to Referral Codes

This migration adds a beneficiary field to the existing referral codes table to track which user should receive benefits when their referral code is used.

Changes

Referral Codes Enhancement

• Adds beneficiary integer field to phoenix_kit_referral_codes table
• Allows tracking which user benefits from referral code usage
• Supports reward/benefit systems for referral programs
• Maintains backward compatibility with existing referral codes

PostgreSQL Support

• Supports PostgreSQL prefix for schema isolation
• Proper field addition with rollback support