fix: Update Python base images to version 3.12 in build configuration

refactor: Improve Dockerfile by adding necessary build tools and cleaning up

fichero_printer/Dockerfile

@@ -1,11 +1,15 @@
 ARG BUILD_FROM
 FROM $BUILD_FROM
 
-# Install Bluetooth system libraries (BlueZ for BLE/RFCOMM)
+# System libraries: BlueZ for BLE/RFCOMM + build tools for numpy & pillow
 RUN apk add --no-cache \
     bluez \
-    bluez-deprecated \
-    dbus
+    dbus \
+    gcc \
+    musl-dev \
+    libjpeg-turbo-dev \
+    zlib-dev \
+    libffi-dev
 
 # Install Python runtime dependencies
 RUN pip3 install --no-cache-dir --break-system-packages \
@@ -16,6 +20,9 @@ RUN pip3 install --no-cache-dir --break-system-packages \
     "uvicorn[standard]>=0.29" \
     "python-multipart>=0.0.9"
 
+# Remove build-only packages to keep the image slim
+RUN apk del gcc musl-dev libffi-dev
+
 # Copy the fichero Python package into the container
 WORKDIR /app
 COPY fichero/ /app/fichero/
@@ -23,8 +30,8 @@ COPY fichero/ /app/fichero/
 # Make the package importable without installation
 ENV PYTHONPATH=/app
 
-# Copy and register the startup script
+# Copy startup script and normalise line endings (Windows CRLF -> LF)
 COPY run.sh /usr/bin/run.sh
-RUN chmod +x /usr/bin/run.sh
+RUN sed -i 's/\r//' /usr/bin/run.sh && chmod +x /usr/bin/run.sh
 
 CMD ["/usr/bin/run.sh"]