fix: use secureFetch for admin verification request

[tanushkat96]

Closes #427

Summary

Updated the admin verification flow to use the new secureFetch utility introduced in PR #380.

Changes

• Imported secureFetch from src/lib/apiClient
• Replaced fetch('/api/auth/verify-admin') with secureFetch('/api/auth/verify-admin') in src/components/auth/AdminKeyModal.tsx

Why

The new CSRF middleware requires mutating API requests to include the CSRF token header. Using secureFetch ensures the required token is automatically attached to the admin verification POST request.

Additional Review

• Reviewed mutating requests (POST, PUT, PATCH, DELETE) within the src directory.
• The admin verification endpoint was the frontend /api/* request requiring migration to secureFetch.
• Other mutating requests found during review were external API calls (e.g. GitHub APIs) or utility/debug scripts and are not affected by the /api/* CSRF middleware.

[Aditya948351]

LGTM! Approved. Great work on this.