Fix npub normalization and improve test coverage

[23bsm038-Mahi]

Summary

Safely handle router.query.npub in marketplace routing.

Fix

• added normalizeNpub helper
• removed unsafe query handling
• improved test coverage (malformed + happy path)

Impact

• prevents runtime errors
• ensures stable routing behavior

This PR contains only relevant changes.

[vercel]

@23bsm038-Mahi is attempting to deploy a commit to the shopstr-eng Team on Vercel.

A member of the Team first needs to authorize it.

[23bsm038-Mahi]

Hi @arnavkirti @GautamBytes

I've created a clean follow-up PR (#335) addressing all review feedback:

• extracted normalizeNpub helper
• restored and updated tests
• added malformed + happy-path test cases
• removed unrelated changes

Would love your review on this one!

[23bsm038-Mahi]

Hi @calvadev @GautamBytes

Just a quick update — this PR is now ready for review.

• Extracted normalizeNpub helper for cleaner and safer handling
• Restored and updated existing tests (no regressions)
• Added focused tests for malformed npub handling
• Added a happy-path test ensuring valid npub triggers nip19.decode

This PR is intentionally kept minimal and scoped only to this issue.

Please let me know if any further refinements are needed. Thanks!

[arnavkirti]

LGTM

[23bsm038-Mahi]

I've updated the client-side npub decoding to ensure strict type validation (checking decoded.type and data type), removed unsafe casting, and kept the changes minimal.
Edge cases like malformed and query-array inputs are now safely handled.
This should now be production-ready and consistent with SSR behavior. Let me know if anything else is needed!