Chore: Use safe-regex to prevent ReDoS in search filter

[pavelzotikov]

Summary

Integrated safe-regex library to validate user-provided regular expressions and prevent potential ReDoS (Regular Expression Denial of Service) vulnerabilities.

Changes

• Added safe-regex to check the safety of user-generated search regex patterns.
• If the input regex is considered unsafe (exponential-time), the search will be rejected or skipped.
• Improves overall stability and security of the search endpoint.

Motivation

User input passed to $regex can introduce catastrophic backtracking. This change ensures that only safe regex patterns are used in database queries.

Notes

• The validation runs before executing the MongoDB query.