Correct allergy-tracking checklist claim about SECURITY.md

[observerr411]

• Location: contracts/allergy-tracking/IMPLEMENTATION_CHECKLIST.md:119
• Problem: Checklist marks SECURITY.md as complete, but that file is absent in contracts/allergy-tracking/.
• Resolution criteria: Either add contracts/allergy-tracking/SECURITY.md or mark checklist accurately.

[AdityaK9822]

@AdityaK9822 has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

I would like to work on this issue.

I’ll resolve the inconsistency by either adding the missing SECURITY.md file under contracts/allergy-tracking/ or updating the checklist to reflect its absence—whichever aligns best with the project’s

ℹ️ Repo Maintainers: To accept this application, review their application or assign @AdityaK9822 to this issue.