* fix(client): restore fixed header height to fix macOS server list scroll

PR #2740 changed root-header from a fixed `height: 64px` to
`min-height: calc(64px + var(--outline-safe-area-top))` with a matching
top padding. On Mac Catalyst `env(safe-area-inset-top)` is non-zero, so
the header grew past 64px while `servers-view` still hard-codes
`height: calc(100vh - 64px)`. That mismatch, combined with the view's
`justify-content: center` and lack of `overflow-y`, pushed the first
server card up under the header and made the list unscrollable once a
few servers were added.

Revert the header to its fixed 64px height to restore correct layout.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* fix(client): keep the safe-area header but subtract the same inset in servers-view (calc(100vh - 64px - var(--outline-safe-area-top))) and add overflow-y: auto

* chore: removed redundant height value from server_view

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Co-authored-by: Sarah Laplante <laplante@getoutline.org>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>