Changelog 04.12 hint for core system and improve documentation

Refactor the entire '/misc' subsystem with a new three-tier defaults architecture and various improvements. Documentation added under '/docs/guides'.

Author: MickLesk

CHANGELOG.md

@@ -14,9 +14,12 @@ Exercise vigilance regarding copycat or coat-tailing sites that seek to exploit
 
 ## 2025-12-04
 
-### 🆕 New Scripts
+### 🛠️ Core Overhaul
 
-  - Three-tier defaults system | security improvements | error_handler | improved logging | improved container creation | improved architecture [@MickLesk](https://github.com/MickLesk) ([#9540](https://github.com/community-scripts/ProxmoxVE/pull/9540))
+  - Major refactor of the entire `/misc` subsystem introducing a secure, modular and fully extensible foundation for all future scripts.  
+    Includes the new three-tier defaults architecture (ENV → App → User), strict variable whitelisting, safe `.vars` parsing without `source/eval`, centralized `error_handler.func`, structured logging, an improved 19-step advanced wizard, unified container creation, dedicated storage selector, updated sysctl handling, IPv6 disable mode, cloud-init library, SSH key auto-discovery, and a complete cleanup of legacy components.  
+    Documentation added under `/docs/guides`.  
+    [@MickLesk](https://github.com/MickLesk) ([#9540](https://github.com/community-scripts/ProxmoxVE/pull/9540))
 
 ### 🚀 Updated Scripts