fix: revisit route guards for verify-email and complete-registration

[aminamos]

Summary:

Resolves #149.
Enhances route guards and ProtectedPageWrapper to verify authentication resolution before redirecting, preserving query parameters and handling edge-case race conditions on registration completion.

Expected behavior:

Users navigating between verify-email and complete-registration are not prematurely redirected to sign-in.

Testing tips:

1. Checkout fix/149-route-guards-verify-complete.
2. Run yarn test.
3. Walk through registration completion flow.

Please make sure these boxes are checked before submitting your pull request - thanks!

• Run the unit tests with yarn test to make sure you didn't break anything
• Add or update any needed documentation to the repo
• Format the title like "feat: [new feature short description]". Title must follow the Conventional Commit Specification(https://www.conventionalcommits.org/en/v1.0.0/).
• Linked all relevant issues
• Include screenshot(s) showing how this pull request works and fixes the issue(s)

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