security: validate incoming API requests

[Abd-Standard]

Description

Add request validation for all API endpoints to prevent invalid or malformed data from reaching the application logic.

Acceptance Criteria
Validation added
Invalid requests rejected
Consistent error messages
Tests included

[Ayinkx]

Hi i would like to work on this issue please assign to me
I can do it perfectly

[susanyusuf]

Hi Maintainer, I would love to tackle this issue. Properly securing API endpoints with robust input validation is critical to keeping the application logic clean and safe from malicious or malformed payloads.

My plan to address the acceptance criteria: Validation Layer: Integrate a clean, schema-based validation middleware (e.g., Zod, Joi, or the repository's existing validator) to intercept and parse incoming payloads before they hit the controller logic.

[grantfox-oss]

🦊 GrantFox — @susanyusuf has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #45)
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 | FWC26 campaign!

@susanyusuf's PR #125 was approved and merged by @Abd-Standard.

🏆 @susanyusuf: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (96 total points). Track your full progress on GrantFox.

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