fix: switch to bullseye base to resolve wkhtmltox dependencies

Dockerfile

@@ -1,5 +1,9 @@
-FROM python:3.11-slim
+# 1. Use 'bullseye' explicitly. 
+# The default 'slim' is now Bookworm (Debian 12), which has dropped support for the older wkhtmltopdf dependencies.
+FROM python:3.11-slim-bullseye
 
+# 2. Install dependencies
+# We include 'xfonts-75dpi' and 'xfonts-base' which are crucial for wkhtmltopdf
 RUN apt-get update && apt-get install -y \
     git \
     git-lfs \
@@ -7,23 +11,24 @@ RUN apt-get update && apt-get install -y \
     libgl1 \
     libglib2.0-0 \
     wget \
-    && apt-get install -y --no-install-recommends \
-       fontconfig \
-       libfreetype6 \
-       libjpeg62-turbo \
-       libpng16-16 \
-       libx11-6 \
-       libxext6 \
-       libxrender1 \
-       libxft2 \
-       libfontconfig1 \
-       xfonts-base \
-       xfonts-75dpi \
-    && wget https://github.com/wkhtmltopdf/packaging/releases/download/0.12.6.1-2/wkhtmltox_0.12.6.1-2.jammy_amd64.deb -O /tmp/wkhtmltox.deb \
-    && apt-get install -f -y /tmp/wkhtmltox.deb \
-    && rm -rf /tmp/wkhtmltox.deb \
+    fontconfig \
+    libfreetype6 \
+    libjpeg62-turbo \
+    libpng16-16 \
+    libx11-6 \
+    libxext6 \
+    libxrender1 \
+    libxft2 \
+    libfontconfig1 \
+    xfonts-base \
+    xfonts-75dpi \
     && rm -rf /var/lib/apt/lists/*
 
+# 3. Download the specific package for BULLSEYE (Debian 11), not Jammy (Ubuntu)
+RUN wget https://github.com/wkhtmltopdf/packaging/releases/download/0.12.6.1-2/wkhtmltox_0.12.6.1-2.bullseye_amd64.deb -O /tmp/wkhtmltox.deb \
+    && apt-get install -f -y /tmp/wkhtmltox.deb \
+    && rm -rf /tmp/wkhtmltox.deb
+
 WORKDIR /app
 
 COPY requirements.txt .