SExI System SQL Scripts and data loading implementation

[lsylkaj]

Overview
This PR implements the Silverbullet Expenses and Invoices (SExI) system using Trino SQL. The implementation processes data from HR and Finance files to create a database structure for tracking employees, expenses, and supplier invoices.
Implementation Details
Data Processing
load_data.py: Processes source data from HR and Finance directories, generating SQL files for database creation and data loading. Handles employee records, expense receipts, and supplier invoices with proper SQL escaping for special characters.
Database Structure
create_employees.sql: Creates the EMPLOYEE table with employee details and management relationships.
create_expenses.sql: Creates the EXPENSE table to track all company expenses with employee attribution.
create_invoices.sql: Creates SUPPLIER and INVOICE tables to manage vendor relationships and payment obligations.
Analysis Queries
find_manager_cycles.sql: Identifies cycles in the management hierarchy that could cause issues with expense approval workflows.
find_employee_expenses.sql: Retrieves detailed expense information for specific employees, including approval chain.
find_employee_managers.sql: Traverses the complete management chain for any employee using recursive CTEs.
calculate_largest_expensors.sql: Identifies employees who have exceeded spending thresholds, including manager information.
generate_supplier_payment_plans.sql: Creates structured payment plans for all suppliers, ensuring invoices are paid before due dates.
Technical Approach
Used recursive Common Table Expressions (CTEs) for hierarchical data analysis
Implemented proper SQL string escaping to prevent injection vulnerabilities
Created modular SQL files for each specific business requirement
Ensured all data is loaded exclusively from provided source files