Update PMDB.Create_Database_Backup.sql

[Imran-imtiaz48]

Improvements Made:

1. Used SYSNAME instead of VARCHAR(50) for database names — it’s more semantically accurate and flexible.
2. Formatted timestamp using FORMAT() for readability.
3. Better username extraction using PARSENAME() to get only the login name.
4. Improved folder logic with fallback/default behavior.
5. Added IF NOT EXISTS to create schema safely.
6. Included WITH INIT, STATS = 10 for better control and visibility during the backup process.
7. Added error handling to notify if the DB doesn’t exist.
8. Readable and reusable variable names to make the procedure self-documenting.