docs: archive outdated reports and organize references

Archived several outdated reports (`Ping-Service_Impl_01-2026.md`, `Frontend_Integration_Status.md`, etc.)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.

docs/90_Reports/Infrastructure_Status_Report_01-2026.md

@@ -1,6 +1,6 @@
 ---
 type: Report
-status: FINAL
+status: ARCHIVED
 owner: DevOps Engineer
 last_update: 2026-01-20
 context: Phase 1-3 (Backend Ready)
@@ -8,6 +8,10 @@ context: Phase 1-3 (Backend Ready)
 
 # Infrastructure Status Report: "Tracer Bullet" Readiness
 
+**ARCHIVED:** This report reflects a past state. Please refer to `2026-01-23_Weekend_Status_Report.md` for the current status.
+
+---
+
 **Datum:** 20. Jänner 2026
 **Autor:** DevOps & Infrastructure Engineer (Updated by Backend Developer)
 **Ziel:** Bestätigung der Einsatzbereitschaft der lokalen Entwicklungsumgebung für Phase 1 (Backend Hardening) und Phase 3 (Sync).