feat(integration): add comprehensive FinaBill sync API and enhance payment processing

[compgeniuses]

Description

• Added FinaBill integration endpoints for managing accounts, bills, suppliers, and expenses
• Implemented listPaymentAccounts and listAccountTransactions for operational money accounts with pagination
• Created upsertAccount, upsertBill, and upsertSupplier mutations with robust externalId matching and fallback logic
• Enabled listBills and listExpenses queries with support for updatedSince filter and external linkage
• Extended bill payment logic to include expense creation and return expenseId
• Enhanced suppliers and accounts upsert to stamp externalSystem as "finabill" and support name-based matching
• Introduced detailed tests for deep sync features covering accounts, bills, suppliers, and expenses synchronization
• Updated API scopes: added bills:read, bills:write, expenses:read, accounts:write with proper permission enforcement
• Modified bills and expenses APIs to include externalId and externalSystem linkage in responses and inputs
• Added linkage of bill externalId to expenses triggered on creation to improve integration data consistency

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Refactor (no functional changes)

How Has This Been Tested?

Please describe the tests that you ran to verify your changes.

• Unit tests
• Integration tests
• End-to-end tests
• Manual testing

Test Configuration:

• Node.js version:
• PostgreSQL version:
• OS:

Checklist:

• My code follows the project's code style
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (if applicable)
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

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Additional context:

Add any other context about the pull request here.