Report missing ComponentScan coverage for top-level providers

[flaringapp]

Summary

Fixes issue #62 by reporting a compile-time error when a local top-level annotated provider function is not covered by any loaded @ComponentScan module and would be missing from the runtime Koin graph.

This also treats core org.koin.dsl.koinApplication as a Koin entrypoint for this diagnostic, matching the existing startKoin behavior and repo test usage.

Verification

./test.sh
./test.sh --tests 'org.jetbrains.kotlin.compiler.plugin.template.runners.JvmErrorMessageTestGenerated'
./test.sh --tests 'org.jetbrains.kotlin.compiler.plugin.template.runners.JvmDiagnosticTestGenerated'
./test.sh --tests 'org.jetbrains.kotlin.compiler.plugin.template.runners.JvmBoxTestGenerated$Toplevel'