fix(deps): add missing mysql2 package for MySQL database support

[eduardomozart]

📋 Description

The application natively supports MySQL as an alternative database backend via Sequelize (configured in server/utils/database.js using DB_TYPE=mysql). However, the required underlying MySQL dialect driver (mysql2) was missing from the package.json dependencies.

If a user configures their environment to use MySQL instead of the default SQLite, the Node.js server crashes on startup with the following error thrown by Sequelize:

Error: Please install mysql2 package manually
    at ConnectionManager._loadDialectModule (/.../node_modules/sequelize/lib/dialects/abstract/connection-manager.js:55:15)
    at new ConnectionManager (/.../node_modules/sequelize/lib/dialects/mysql/connection-manager.js:30:21)

This PR adds "mysql2": "^3.17.4" to the primary package.json dependencies and updates the yarn.lock file accordingly. This ensures the MySQL driver is present out-of-the-box for any environment that configures DB_TYPE=mysql, preventing instant runtime crashes.

🚀 Changes made to ...

• 🔧 Server
• 🖥️ Client
• 📚 Documentation
• 🔄 Other: ___

✅ Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have looked for similar pull requests in the repository and found none
• This pull request does not contain translations (translations are managed through Crowdin)

🔗 Related Issues

Closes #1098

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

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