Fix sidebar activeHref not being set on full page reload

[mendaomn]

Description

This PR fixes the following scenario:

• full page reload of the / page
• sidebar active item not being highlighted

Changes

• derive activeHref from the pathname at every location change

How Has This Been Tested?

• full page reload
• navigation through all sections
• full page reload of deep nested path (/clusters/{clustername})

PR Quality Checklist

• I added tests to new or existing code
• I removed hardcoded strings and used our i18n solution instead (see here)
• I checked that infrastructure/update_infrastructure.sh runs without any error
• I checked that npm run build builds without any error
• I checked that clusters are listed correctly
• I checked that a new cluster can be created (config is produced and dry run passes)
• I checked that login and logout work as expected

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