Fix ghost button hover contrast

[niemyjski]

Summary

• Fixes the shared ghost Button hover state using the existing semantic accent theme tokens.
• Overrides the Button base's intentional border-transparent only on ghost hover with accent-foreground/40.
• Keeps the change limited to variant="ghost"; the transparent resting state and every other Button variant remain unchanged.

Root cause

The pagination Next control is a shared Button with variant="ghost". It does not have a Next-specific transparency class:

• Every Button starts with border border-transparent so filled, link, and ghost variants do not gain an unintended resting border.
• The old ghost hover used dark:hover:bg-muted/50 and left that border transparent.
• On the dark page background, that half-opacity fill did not provide a clear hover boundary.

The fix belongs in the shared ghost hover variant: it uses the theme's accent hover surface and overrides the transparent border while hovered. Changing the base transparency would incorrectly add borders to unrelated Button variants.

Screenshots

Before — dark-mode Next hovered

After — dark-mode Next hovered

Verification

• Authenticated local /next/stack capture at 1280×577 with the real Next pagination button confirmed in :hover.
• Confirmed the real Next button is a BUTTON using variant="ghost": at rest its background and border both compute to transparent; on hover the shared variant overrides both.
• Rendered hover state: fill rgb(26, 31, 36), border rgb(91, 94, 99), foreground rgb(230, 237, 243).
• The rendered border has 3.14:1 contrast against the dark page background (rgb(2, 5, 10)).
• Audited all shared Button variants and ghost Button call sites; no other Button variant's hover styling changes.
• npm run validate

[github-actions]

Package	Line Rate	Branch Rate	Complexity	Health
Exceptionless.Core	74%	66%	9634	➖
Exceptionless.AppHost	38%	40%	139	❌
Exceptionless.Insulation	37%	35%	286	❌
Exceptionless.Web	84%	68%	6949	✔
Summary	77% (22991 / 29857)	66% (10588 / 16090)	17008	✔