chore(deps-major): migrate @sveltejs/vite-plugin-svelte to 7.1.2 2026-06-24

[Copilot]

Major bump of @sveltejs/vite-plugin-svelte from v5 to v7, which requires vite v8 as a peer. svelte was already at ^5.56.3 (v7 peer requires ^5.46.4), so only two version changes are needed.

Dependency changes

• @sveltejs/vite-plugin-svelte: ^5.0.3 → ^7.1.2
• vite: ^6.3.5 → ^8.0.0 (v7 peer: vite ^8)

No code changes required

• @sveltejs/kit@2.65.0 already lists ^7.0.0 as a valid peer for the plugin
• vitest@^4.1.8 declares vite ^6 || ^7 || ^8 peer support — no vitest bump needed
• v7 introduces no API-level breaking changes affecting this codebase (vitePreprocess() and sveltekit() plugin usage unchanged)

Original prompt

Migrate the dependency '@sveltejs/vite-plugin-svelte' to 7.1.2 on a new branch and open ONE pull request titled 'chore(deps-major): migrate @sveltejs/vite-plugin-svelte to 7.1.2 2026-06-24'. This is a KNOWN BREAKING major bump — work through the migration carefully using this assessment as the spec:

v7 peers vite ^8 + svelte ^5.46.4; project has svelte 5.28.2 + vite 6 → both unsatisfied. SvelteKit 2.65 allows plugin ^7 + vite ^8. Migration: bump svelte→^5.46.4, vite→8, then plugin→7 atomically; run build + vitest.

Apply the code changes the breaking changes require, run the project's install + test/build, and make sure it is green before opening the PR. Keep the change scoped to THIS migration only (do not bump unrelated dependencies, do not refactor). Do NOT merge.