Fix#70: Make medication product fields mandatory

[mercy-korir600]

This PR makes key medication product fields mandatory in the Medication Product module to improve data completeness and prevent incomplete medication records from being submitted.

Changes Made

• Made Generic Name mandatory.
• Made Brand/Product Name mandatory.
• Made **Dose, frequency, duration, route ** mandatory.
• Added validation to prevent submission when any of the required fields are left blank.

Expected Behaviour
Users should not be able to submit a medication product record if any of the required fields are empty.

Testing

• Tested the medication product form with all required fields populated.
• Tested submission with individual required fields left blank.
• Confirmed that incomplete records are prevented from being submitted.
• Confirmed that valid medication product records can still be submitted successfully.