Migrate to detekt 2.x to remove Gradle 10 deprecation warnings #225

Summary

The repo is still on detekt 1.23.8 and Gradle's problems report shows a deprecation warning coming from the detekt plugin:

• The ReportingExtension.file(String) method has been deprecated.
• plugin id: io.gitlab.arturbosch.detekt

This is one of the remaining Gradle 10 deprecation warnings after the Kotlin 2.4 / warning cleanup pass.

Current evidence

• Version catalog entry in /Users/nek/Developer/FlowMVI/gradle/libs.versions.toml:
  • detekt = "1.23.8"
• Gradle problems report from clean assemble:
  • /Users/nek/Developer/FlowMVI/build/reports/problems/problems-report.html
• Problems report identifies:
  • The ReportingExtension.file(String) method has been deprecated.
  • location plugin id: io.gitlab.arturbosch.detekt

Goal

Migrate FlowMVI from detekt 1.x to detekt 2.x and clear the related Gradle 10 deprecation warnings.

Notes

• This is distinct from the Kotlin 2.4 / AGP 9 migration issue.
• The warning appears to come from detekt internals, so local project cleanup on 1.23.x is not the real fix.
• Validate against the current Gradle line (9.5.1) and project build conventions.