Add Program/Module Tag Validation (Uniqueness & Alphanumeric Security)

## 🎯 Issue Description

This issue addresses a security and data integrity gap in the Mentorship Portal where Program and Module tags currently lack validation. They can be duplicated and may contain potential security risks or inconsistent formatting.
Reference: https://github.com/OWASP/Nest/issues/2701

## 📋 Current Issues

1. **No Uniqueness Validation**: Tags can be duplicated within a single entry (e.g., `["python", "python"]`).
2. **No Format Security**: There is no restriction on tag characters, allowing special characters or potentially unsafe strings.
3. **Data Inconsistency**: Lack of standardization allows for mixed naming conventions (e.g., `["Python", "python"]`).

## 🛠️ Proposed Fix

- Update `CreateProgramInput`, `UpdateProgramInput`, `CreateModuleInput`, and `UpdateModuleInput` to implement validation logic for the `tags` field.
- Enforce uniqueness: Ensure the list of tags contains no duplicates.
- Enforce alphanumeric format: Restrict tags to `a-z`, `A-Z`, and `0-9` using regex validation.
- Add comprehensive unit tests to verify that invalid or duplicate tags are correctly rejected.

**Are you going to work on implementing this?**

- [x] Yes
- [ ] No