initial solution added

[Stiv90]

This pull request contains the full rebuild of the SExI system, as described in the task brief. The project uses Trino with an in-memory database via Docker, and includes:

What’s Included:

Employee data (create_employees.sql)
Created EMPLOYEE table and populated from employee_index.csv
Expense records (create_expenses.sql)
Parsed semi-structured text receipts and inserted into EXPENSE table
Invoice and Supplier data (create_invoices.sql)
Extracted invoice info from text files
Generated unique supplier_ids and calculated due_dates
Analysis queries
find_manager_cycles.sql: Detects circular reporting lines in management
calculate_largest_expensors.sql: Lists employees who expensed >1000
generate_supplier_payment_plans.sql: Computes monthly payment plan for invoices

Tests

Test queries and expected outputs are included in the /tests folder

README.md explains how to run and verify them using Trino