Add Ollama as a auth provider in onboarding with Cloud + Local mode
selection, browser-based sign-in via /api/me, smart model suggestions
per mode, and graceful fallback when the default model is unavailable.
- Extract shared ollama-models.ts
- Auto-pull missing models during onboarding
- Non-interactive mode support for CI/automation
Closes#8239Closes#3494
Co-Authored-By: Jeffrey Morgan <jmorganca@gmail.com>