docs: fix broken Next.js compiler documentation link

[Pranav-0440]

🧩 Summary

This PR fixes a broken documentation link related to the Next.js compiler guide.

❌ Problem

The documentation previously pointed to:
https://lingo.dev/en/compiler/frameworks/nextjs

This path no longer exists and resulted in a 404 error.

✅ Fix Applied

Updated all references to use the correct documentation route:
https://lingo.dev/en/compiler/frameworks/nextjs-app-router

🧠 Why this matters

• Prevents users from landing on a broken page
• Ensures developers can find the correct Next.js integration docs
• Improves documentation accuracy and usability

🔍 Verified

I searched the codebase for frameworks/nextjs to ensure all outdated links were corrected.

[sumitsaurabh927]

cc: @davidturnbull

[Pranav-0440]

Hi team 👋,
The branch has now been updated with the latest main changes. ✔️

The failing CI check appears unrelated to this PR since all modifications are documentation updates. Everything is ready for review.

Please let me know if any further changes are needed!

[Pranav-0440]

All checks passing ✔️
PR ready for review.

[github-actions]

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