refactor: Rename database index from `idx_timestamp` to `idx_created_at`, improve seed script with intended duplicate transactions and increased delays, and update documentation.

feat: add transaction seeding script, include favicon, and remove deprecated public folder reference from README.

feat: Replace vanilla JavaScript frontend with Simple React (Vite) application, update server logic.

feat: Add transaction data seeding script, enhance health check with database status, and update README.

feat: add initial README.md detailing project setup, architecture, fraud rules, and scaling considerations.

feat: Implement a basic frontend user interface for the transaction risk monitoring system and configure the server to serve static assets.

feat: Implement dashboard statistics endpoint with a new database function to retrieve transaction metrics.

feat: Add endpoint to retrieve all transactions and implement database function to fetch them.

feat: implement initial transaction risk monitoring system with Express server, SQLite database, and risk evaluation engine.