Small improvements after upgrading to .NET 9, React 19, and Lingui v5

[tjementum]

Summary & Motivation

Introduce a series of small improvements following upgrades to .NET 9, React 19, and Lingui v5, as well as a few adjustments for better project consistency.

Improvements related to the upgrades:

• Replace useFormState from ReactDOM with useActionState in React 19.
• Fix missing Lingui macro imports to comply with Lingui v5 guidelines.
• Update the README to reflect .NET 9, C# 13, React 19, and the latest project structure.

Additional adjustments:

• Use [AsParameters] in Minimal API GET endpoints for automatic query binding, replacing manual instantiation.
• Update the Issuer and Audience for Token signing to use "Localhost" instead of "https://localhost:9000"

Checklist

• I have added a Label to the pull-request
• I have added tests, and done manual regression tests
• I have updated the documentation, if necessary

[linear]

PP-278 Small improvements after upgrading to .NET 9, React 19, and Lingui v5

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
50.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud