refactor: centralize transcription model display typing

[RutamBhagat]

Summary

• extract Whisper/Parakeet model display fallback helpers into src/utils/transcriptionModelDisplayInfo.ts
• update pickers to consume typed helpers instead of inline fallback objects
• make createExternalLinkHandler generic over HTMLElement so handler typing matches varied click targets

Stacked PR Context

This PR depends on fix/typecheck-2 and should be reviewed after that PR.

Depends on #210

Output

npm run typecheck

Found 12 errors in 6 files.

Errors  Files
     3  src/components/SettingsPage.tsx:1447
     4  src/components/TitleBar.tsx:41
     1  src/components/ui/MarkdownRenderer.tsx:12
     1  src/helpers/llamaCppInstaller.ts:8
     1  src/lib/neonAuth.ts:119
     2  src/services/ReasoningService.ts:17