Refactor IPv6 disable logic and add 'disable' option

Replaces previous IPv6 disabling method with a dedicated 'disable' option, storing sysctl settings in /etc/sysctl.d/99-disable-ipv6.conf. Updates build and install scripts to clarify the difference between 'none' (no assignment) and 'disable' (fully disables IPv6), adds user warnings, and disables IPv6 listeners in nginx if present.

CHANGELOG.md

@@ -12,12 +12,6 @@ Exercise vigilance regarding copycat or coat-tailing sites that seek to exploit
 
 ## 2025-11-21
 
-### 🚀 Updated Scripts
-
-  - #### 🔧 Refactor
-
-    - Refactor IPv6 disable logic and add 'disable' option [@MickLesk](https://github.com/MickLesk) ([#9326](https://github.com/community-scripts/ProxmoxVE/pull/9326))
-
 ## 2025-11-20
 
 ### 🚀 Updated Scripts