luci-app-upnp: add second CGNAT UCI option

Alternative option to STUN allow-filtered. As requested by AquanJSW, to
test with Tailscale. Also adds the required daemon fix. No STUN public
IPv4 detection; various issues, e.g. with PCP/NAT-PMP clients

(proposed for inclusion, to merge with prior)

Signed-off-by: Self-Hosting-Group <selfhostinggroup-git+openwrt@shost.ing>

Author: Self-Hosting-Group

applications/luci-app-upnp/htdocs/luci-static/resources/view/upnp/upnp.js

@@ -174,6 +174,7 @@ return view.extend({
 		o.value('', _('Disabled'), _('Manually override external IPv4 to allow a private IP'));
 		o.value('1', _('Enabled'), _('Filtering test currently requires an extra firewall rule'));
 		o.value('allow-filtered', _('Enabled') + ' (' + _('allow filtered') + ')', _('Allow filtered IPv4 CGNAT test result'));
+		o.value('allow-private-ext-ipv4', _('Ignore') + ' (' + _('allow private, avoid') + ')', _('No STUN public IPv4 detection; various issues'));
 		o.optional = true;
 
 		o = s.taboption('advanced', form.Value, 'stun_host', _('STUN server'));