Change PostgreSQL to MySQL throughout the project

[Copilot]

This PR changes the database system from PostgreSQL to MySQL throughout the project. The following changes were made:

Docker Configuration

• Updated docker-compose.yml to use MySQL 8 instead of PostgreSQL 14
• Changed environment variables from PostgreSQL format to MySQL format
• Updated volume mount paths to use MySQL standard locations

SQL Script

• Modified init_db.sql to be compatible with MySQL syntax:
  • Changed SERIAL types to INT AUTO_INCREMENT
  • Updated timestamp handling with ON UPDATE CURRENT_TIMESTAMP
  • Modified foreign key syntax to match MySQL requirements
  • Added backticks for MySQL reserved words (like condition)
  • Adjusted default value syntax for MySQL compatibility

Documentation

• Updated all PostgreSQL references in README.md to MySQL
• Changed connection strings from postgresql:// protocol to MySQL format
• Updated port references from 5432 to 3306
• Changed MCP server configuration examples to use MySQL

These changes should allow users to run the project with MySQL while maintaining the same functionality.

Fixes #2.

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.