0.0.0.0/0 already includes 192.168.0.0/16 However if your VPN doesn’t have an “exit node” configure (it’s Tailscale’s name for it but basically it means that there’s no machine configured to connect your tunnel to Internet) there could be issues with retrieving DNS.
I’d suggest making AllowedIP ip your-vpn-net, 192.168.y.0/24
Problem with that setup would be that while on your network with VPN turned on there could be conflicts.
Other solution would be to host a pihole on your wireguard network, use pihole’s wg ip as DNS server in wg configs and in pihole create A record for your servers wg ip and domain name.
The easy solution is to add portainer to Traefik using file provider (so file dynamic configuration). This way also allows to add to Traefik services outside of docker itself, so cockpit for example.