fix(saved-materials): validate user and material route params

[om-dev007]

Summary

Added route parameter validation for saved materials endpoints to prevent malformed IDs from reaching authorization and database logic.

Changes made

• Added validation middleware for id and materialId route parameters

• Enforced positive integer validation for saved materials route params

• Applied the validator to both:

  • toggle save endpoint
  • get saved materials endpoint

• Normalized controller param handling to use numeric IDs consistently in authorization and database queries

Benefits

• Returns 400 Bad Request for malformed route parameters
• Prevents invalid IDs from reaching the ORM layer
• Makes error behavior more predictable and improves controller safety

Issue fixed

Closes #305

[vercel]

@om-dev007 is attempting to deploy a commit to the Mohit Yadav's projects Team on Vercel.

A member of the Team first needs to authorize it.

[om-dev007]

@BHUVANSH855 please review this pr