chore(types): add vite/client triple-slash for CSS side-effect imports

TypeScript 5.9 (and the upcoming Vite 8 / plugin-react 6 toolchain)
flags side-effect CSS imports as TS2882 unless ambient declarations
are in scope. Pull in Vite's bundled types so main.tsx's CSS
imports — and the rest of Vite's import-meta.env / ?url / ?raw
helpers — are recognized.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: ystemsrx

src/vite-env.d.ts

@@ -0,0 +1 @@
+/// <reference types="vite/client" />