fix: add Vite client type declarations

[RutamBhagat]

Summary

• add src/vite-env.d.ts with /// <reference types="vite/client" />
• ensures Vite-provided client globals/types resolve cleanly during type-checking

Stacked PR Context

This PR depends on the changes in fix/typecheck and should be reviewed after that PR.

Depends on #208

Output

npm run typecheck

Found 28 errors in 12 files.

Errors  Files
     1  src/components/ControlPanel.tsx:117
     1  src/components/LocalWhisperPicker.tsx:168
     3  src/components/SettingsPage.tsx:1447
     4  src/components/TitleBar.tsx:41
     5  src/components/TranscriptionModelPicker.tsx:47
     1  src/components/ui/MarkdownRenderer.tsx:12
     4  src/components/ui/SupportDropdown.tsx:20
     1  src/helpers/llamaCppInstaller.ts:8
     1  src/hooks/useLocalModels.ts:49
     4  src/hooks/useModelDownload.ts:123
     1  src/lib/neonAuth.ts:119
     2  src/services/ReasoningService.ts:17