Archived several outdated reports (`Ping-Service_Impl_01-2026.md`, `Frontend_Integration_Status.md`, etc.) and added archival notes and references to updated documents. Introduced a centralized reference structure for tech stack documentation, consolidating files under `01_Architecture/Reference/Tech_Stack`. Added new resources (`Gradle_Kotlin_DSL_Primer`, `Kotlin_2-3-0_ReleaseNotes`) for improved project organization and clarity.
