Change the continue button variant from 'outline' to 'default' to
improve visibility in dark mode. The outline variant had poor contrast
against the green success background in dark mode.

#skip-bugbot

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## Summary by cubic
Improve dark mode contrast for the Supabase success state by switching
the “Continue” button from outline to default. Also adjust success card
and integrate prompt colors for better readability in dark mode.

<sup>Written for commit f184afad3d02c069b4a33a6b5f9eeb4dca65c3ec.
Summary will update on new commits.</sup>

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Co-authored-by: Claude <noreply@anthropic.com>