Fix wrong navbar height on 404 pages

[EverStarck]

On mobile the --navbar-height css var is set to 1585px adding lot of scroll to find 404 text

this PR fixes it. co-authored by Opus 4.6 btw

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While making the commit I was getting

Running smoke tests against http://localhost:57756

  ✓ home page
  ✗ query docs: HTTP 500
  ✗ router docs: HTTP 500
  ✗ table docs: HTTP 404

1 passed, 3 failed

but I checked main branch and also having the same test issue.

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