Migrate to Vite 8 stable and update frontend tooling deps

[Copilot]

Replaces the rolldown-vite pre-release shim with the official Vite 8.0.0 stable release and updates all related dependencies.

Dependency updates

• vite: npm:rolldown-vite@latest → ^8.0.0 (official)
• @sveltejs/vite-plugin-svelte: ^6.x → ^7.0.0 (Vite 8 peer requirement)
• vitest: 4.0.18 → ^4.1.0
• vite-plugin-oxlint: ^1.6.0 → ^2.0.1
• oxlint / eslint-plugin-oxlint: ^1.48.0 → ^1.55.0
• oxfmt: ^0.33.0 → ^0.40.0
• Storybook packages: ^10.2.8 → ^10.2.19

Cleanup

• Removed vite entry from overrides in package.json (no longer aliasing to rolldown-vite)
• Added legacy-peer-deps=true to .npmrc — @storybook/addon-svelte-csf@5.0.11 still declares vite@"^5||^6||^7" in its peer deps and hasn't released a fix; this unblocks npm ci without downgrading

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[github-actions]

Package	Line Rate	Branch Rate	Complexity	Health
Exceptionless.Insulation	24%	23%	208	❌
Exceptionless.Core	66%	59%	7446	➖
Exceptionless.AppHost	26%	14%	55	❌
Exceptionless.Web	55%	42%	3489	➖
Summary	61% (11861 / 19532)	53% (5656 / 10706)	11198	➖