Support definition annotations on objects via INSTANCE

[exoego]

Closes #77

A definition annotation (e.g. @Single) on a Kotlin object made the plugin emit a constructor call for the object. An object has no public constructor, so this produced invalid IR. With compiler assertions on, it failed lowering with an AssertionError. With assertions off, it compiled and then crashed at runtime with NoSuchMethodError, while Gradle still reported BUILD SUCCESSFUL.

The definition body now references the singleton INSTANCE with irGetObject when the target is an object. This mirrors the existing object handling in ModuleFunctionResolver.buildModuleGetCall. Both the annotation path (DefinitionCallBuilder.createDefinitionLambda, used by the root and scoped builders) and the DSL path (KoinDSLTransformer.handleTypeParameterCall for single() and friends) are covered. Interface binding on an object still emits the .bind() chain around the INSTANCE reference.

Tests

• box/annotations/object_binding.kt mirrors the real use case from the issue. An object is bound to a framework interface with @Single([Loader::class]), extends a shared abstract base, and is collected through the interface with getAll. It fails on the unfixed plugin with an IR validation error and passes after the fix.
• box/annotations/object_singleton.kt is the minimal @Single object case.
• box/dsl/single_object.kt covers the same case for single().
• playground-apps/app-kmp-klib adds an interface-bound @Single object so the change is compiled on the KLIB targets iosArm64 and wasmJs.

Docs updated to note that objects are supported and resolve to INSTANCE.