[#14360] Replace hard-coded query param keys

[aishwaryabandapelly-ai]

Summary

Part of #14360.

This PR replaces remaining hard-coded shared backend query parameter keys in the frontend with the existing QueryParamKeys constants from api-const.ts.

Changes

• Replaced hard-coded courseid usage with QueryParamKeys.COURSE_ID
• Replaced hard-coded key usage with QueryParamKeys.KEY
• Replaced hard-coded nextUrl usage with QueryParamKeys.NEXT_URL
• Replaced hard-coded accountid usage with QueryParamKeys.ACCOUNT_ID
• Replaced hard-coded userid usage with QueryParamKeys.USER_ID

Notes

I intentionally left unrelated keys such as entityType, instituteid, and status unchanged because they are not currently exposed in QueryParamKeys or are outside the scope of this small change.

Testing

• Ran git diff --check
• Verified hard-coded shared query param strings are no longer present in the changed frontend/service files
• Did not run frontend lint/build locally because dependencies were not installed

[aishwaryabandapelly-ai]

All required checks are passing now. Please let me know if any changes are needed. Thank you!