luci-proto-wireguard: add IPv6 routed prefix (ip6prefix) support

Add support for IPv6 routed prefix (ip6prefix) in the General Settings
tab of WireGuard interfaces, similar to other protocols like 6in4.

This allows users to configure Prefix Delegation for WireGuard
interfaces through LuCI, enabling proper IPv6 SLAAC delegation
to downstream clients.

Changes:
- Add ip6prefix DynamicList option to general tab
- Remove duplicate ip6prefix from advanced tab

Signed-off-by: Maksym Vasylchenko <nahual15@gmail.com>

Author: nagual2

protocols/luci-proto-wireguard/htdocs/luci-static/resources/protocol/wireguard.js

@@ -157,6 +157,10 @@ return network.registerProtocol('wireguard', {
 		o.datatype = 'ipaddr';
 		o.optional = true;
 
+		o = s.taboption('general', form.DynamicList, 'ip6prefix', _('IPv6 routed prefix'), _('IPv6 prefix routed to this interface for use by clients. Use this for Prefix Delegation.'));
+		o.datatype = 'cidr6';
+		o.optional = true;
+
 		o = s.taboption('general', form.Flag, 'nohostroute', _('No Host Routes'), _('Optional. Do not create host routes to peers.'));
 		o.optional = true;
 
@@ -182,9 +186,6 @@ return network.registerProtocol('wireguard', {
 			return true;
 		};
 
-		o = s.taboption('advanced', form.DynamicList, 'ip6prefix', _('IPv6 routed prefix'), _('This is the prefix routed to you by your provider for use by clients'));
-		o.datatype = 'cidr6';
-
 		// -- peers -----------------------------------------------------------------------
 
 		try {