docs: remove completed migration tracking notes

[BreadGenie]

Will clean up the readme later

[greptile-apps]

Confidence Score: 5/5

This looks safe to merge.

• No blocking issues found in the changed docs.
• Remaining README links point to files that still exist.
• No Frappe backend, frontend runtime, permissions, hooks, or SQL paths changed.

Important Files Changed

Filename	Overview
README.md	Removed WIP migration status text and narrowed setup guidance to current docs.
frontend/src/apps/README.md	Removed migration-era references and kept current Suite SPA conventions.
monorepo.md	Deleted completed migration tracking notes.

_{Reviews (1): Last reviewed commit: "docs: remove completed migration trackin..." | Re-trigger Greptile}