Write a function `formatDate` that takes a timestamp (number or string) and returns the date in this format:
`hh:mm AM/PM, DD/MM/YYYY`
Input: timestamp = 1716281220000 // corresponds to 21 May 2025, 15:47:00
Output: "03:47 PM, 21/05/2025"
Explanation: Converted to 12-hour format with AM/PM and proper day/month formatting.