frontend: OauthPopup: Fix typos and use console.error

[NAME-ASHWANIYADAV]

Fixes #5053

Summary

Fix two error catch blocks in OauthPopup that had the typo "occured" (should be "occurred") and were using console.log instead of console.error for error conditions.

Changes

• Fix typo: "occured" → "occurred" in both error messages
• Change console.log to console.error for proper error severity
• Capitalize error messages consistently

Steps to Test

1. Trigger OIDC auth flow that opens the OAuth popup
2. Open browser DevTools → Console → filter by "Errors"
3. Verify error messages appear correctly if the popup fails

[k8s-ci-robot]

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[NAME-ASHWANIYADAV]

/assign @illume

[NAME-ASHWANIYADAV]

@illume Hi, could you please review this whenever you have some free time?