fix(security): resolve IP extraction bypass flaw in rate limiter

[ArshVermaGit]

Description

This PR addresses a critical flaw in the IP extraction logic within the contact rate limiter (src/lib/contact-rate-limit.ts).

Previously, the logic used an improper short-circuit evaluation:
`(req.headers.get("x-forwarded-for") || req.headers.get("x-real-ip") || "127.0.0.1") ?? ...`
Because "127.0.0.1" is a truthy string, this expression would always evaluate to 127.0.0.1 if an x-forwarded-for header was missing, entirely bypassing the extraction of x-real-ip and making the rate limiter trivial to spoof or bypass. It also failed to correctly extract the originating client IP when x-forwarded-for contained a comma-separated list of proxies.

Resolved Issue

Resolves #1788

Changes Made

• Robust IP Extraction: Rewrote getContactClientIp to properly prioritize the IP resolution chain:
  1. req.ip (Standard NextRequest IP, cast safely to resolve TS typing issues)
  2. First address in x-forwarded-for (properly split and trimmed)
  3. x-real-ip
  4. Fallback cleanly to "unknown" instead of hardcoding localhost.
• Type Safety: Ensured that the fallback logic appeases the TypeScript compiler for Next.js 15+ environments where NextRequest typing for .ip can be strict/missing.

Impact

• Security: The contact endpoint is now properly protected against IP spoofing and rate-limit bypasses. Malicious users can no longer circumvent the limiter by manipulating headers.

Testing

• Ran the rate limit unit test suite (npm run test test/contact-rate-limit.test.ts).
• Verified that tests previously failing due to incorrect parsing now pass with a 100% success rate.

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[ArshVermaGit]

Hi @Priyanshu-byte-coder ! Issue #1788 has been resolved. Please review the PR and merge it under GSSoC. Thanks!