fix(cistech-tunnel): reset DNS and clean tun interface before connecting

apps/cistech-tunnel/shared/openconnect-vpn

@@ -376,6 +376,14 @@ connect_vpn() {
     # Kill any existing VPN processes
     kill_vpn_processes
 
+    # Reset DNS to public servers (VPN script may have overwritten it)
+    log DEBUG "Resetting DNS to public servers..."
+    echo "nameserver 8.8.8.8" > /etc/resolv.conf
+    echo "nameserver 1.1.1.1" >> /etc/resolv.conf
+
+    # Clean up stale tun interface
+    ip link delete tun0 2>/dev/null || true
+
     # Validate required variables
     if [[ -z "$VPN_HOST" ]]; then
         log ERROR "VPN_HOST is not set"