\documentclass{article}
\usepackage[paperwidth=90mm,paperheight=55mm,margin=0mm]{geometry}
\usepackage{tikz,qrcode,graphicx,xcolor,lmodern}
\usepackage{wrapfig}
\usetikzlibrary{calc}        % lets us position the white patch precisely

% ------------------ settings you might tweak ------------------
\newcommand*{\iconfile}{android-chrome-512x512.png}
\newcommand*{\iconwidth}{23mm}

\newcommand*{\qrurl}{https://abaj.ai}
\newcommand*{\qrsize}{23mm}   % black square (module area)
\newcommand*{\quiet}{1mm}     % quiet zone each side   ‹— now very small
% --------------------------------------------------------------

\begin{document}
% ---------------- FRONT ----------------
\begin{tikzpicture}[remember picture,overlay]
  \node at (current page.center)
        {\includegraphics[width=\iconwidth]{\iconfile}};
\end{tikzpicture}

\clearpage
% ---------------- BACK -----------------
\noindent
\begin{minipage}{\textwidth}
\fontsize{3}{3.5}\selectfont
\ttfamily
\color{gray!70}

% Create invisible space for the QR code in the center
\newlength{\qrtotalsize}
\setlength{\qrtotalsize}{\qrsize}
\addtolength{\qrtotalsize}{2\quiet}

% Position the QR area as a float in the center
\begin{wrapfigure}{r}{0.5\textwidth}
\vspace{-\baselineskip}
\centering
\phantom{\rule{\qrtotalsize}{\qrtotalsize}}
\vspace{-\baselineskip}
\end{wrapfigure}

\input{wallpaper.txt}
\end{minipage}

% Overlay the actual QR code
\begin{tikzpicture}[remember picture,overlay]
  % solid white patch: side = qrsize + 2·quiet
  \path[fill=white]   
    ($(current page.center)+(-\qrsize/2-\quiet,-\qrsize/2-\quiet)$)
      rectangle
    ($(current page.center)+(\qrsize/2+\quiet,\qrsize/2+\quiet)$);

  % QR code on top of the white patch
  \node at (current page.center)
        {\qrcode[height=\qrsize]{\qrurl}};
\end{tikzpicture}
\end{document}