[DRAFT] Organize frontend + add rxjs/vueuse for board sessions + cleanup

[girlnotbird]

@mccolljr I integrated your suggestions from the last PR for this branch into this one.

This merge would:

• add task reinstall command to taskfile.yml (you did this, actually)
• use Logger utility in backend/src/main.ts
• Introduce schemas and types for BoardEvents (not locked into this, it's just one possible shape for P2P communication)
• Add vueuse, rxjs libraries for streaming event data between clients
• Add jsdom and update vitest dependencies for testing
• Refactor frontend/src/App.vue into BoardSession.vue and BoardView.vue
• Break session handling logic into composable useBoardSession() in BoardSession.ts
• Break cursor behavior, coordinate conversion, and view-offset behavior into their own files (I left re-integrating these functions into the BoardView.vue component for another PR focused on the view)
• Introduce a partial spec file for BoardSession.ts (currently only has some testing wrapping rxjs functions)

Looking forward to your review.

[mccolljr]

Sweet, thanks for this. I'll take a look a little later this evening, after dinner