Finance Accounting Module – Complete CRUD, Journals & Seeding

[Anandika-M]

This PR adds the complete Finance Accounting module.

Included:

• ER-compliant models, schemas, repositories, services, controllers, and routers
• Full CRUD for all finance entities
• Auto journal posting for invoices, payments, and depreciation
• Strict cross-module FK usage (Patient, User, Department not duplicated) not implemented yet but added
• Seed script for end-to-end verification

Tested via:

• Swagger API testing
• Seed script execution
• Database integrity checks