[WIP] Refactor communication domain to use FastAPI and SQLModel

[Copilot]

Cloud agent has begun work on Continue the work of... and will update this pull request as work progresses.

Original prompt

Continue the work of #2 :
Take communication, account domain as reference, finishing the refactor of getting rid of BlueFirmament with FastAPI and SQLModel in:

• communication/managers/message/approval.py
• communication/managers/notification/
• main domain managers, schemas

Notes:

• You don't need to follow the existing implementation pattern. You can refactor from an overall perspective that user experience (API endpoints) remains unchanged is the only goal.

The user has attached the following file paths as relevant context:

• .github\instructions\index.instructions.md

Created from VS Code via the GitHub Pull Request extension.

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.