[Security] Implement Audit Trail for Template Modifications

[Abd-Standard]

Description

Track changes made to notification templates for accountability.

Acceptance Criteria
Update history is recorded.
Actor and timestamp are stored.
Audit records are immutable.

[Kappa16]

Hi maintainer...I can work on this issue professionally and make sure this issue is fixed without errors

[Jayydy]

Hello, can i be assigned to this issue?

[Marvy247]

I've reviewed the issue description, and I'm confident I can implement all the requested details smoothly.​ Please assign this issue to me! I can have a PR ready for review in a few hours.
Thank You.

[Ved-viraj]

Hi, can I be assigned this issue please? I’ve gone through the issue carefully and I’m up for the task, kindly assign me please

[grantfox-oss]

🦊 GrantFox — @Ved-viraj has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #106)
2. Your PR will be reviewed by the Core-Foundry maintainers

Good luck! Track your progress on GrantFox.

[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Official Campaign campaign!

@Ved-viraj's PR #164 was approved and merged by @Abd-Standard.

🏆 @Ved-viraj: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (436 total points). Track your full progress on GrantFox.

👏 Great work, @Ved-viraj! Keep contributing to Core-Foundry.