Update Dockerfile

Dockerfile

@@ -1,6 +1,21 @@
 # Use an official Python runtime as a parent image
 FROM python:3.9-slim
 
+# Set environment variables to ensure Python output is unbuffered (helps with logging)
+ENV PYTHONUNBUFFERED=1
+
+# Install system dependencies that might be needed by Pillow or other libraries
+# gcc and python3-dev are for compiling C extensions if wheels are not available
+# libjpeg-dev, zlib1g-dev are common for Pillow's JPEG and PNG support
+# build-essential includes gcc, g++, make, etc.
+RUN apt-get update && apt-get install -y --no-install-recommends --fix-missing \
+    build-essential \
+    python3-dev \
+    libjpeg-dev \
+    zlib1g-dev \
+    && echo "System dependencies installed." \
+    && rm -rf /var/lib/apt/lists/*
+
 # Set the working directory in the container
 WORKDIR /app
 
@@ -8,19 +23,26 @@ WORKDIR /app
 COPY requirements.txt .
 
 # Install any needed packages specified in requirements.txt
-# --no-cache-dir reduces image size, --upgrade pip ensures pip is up-to-date
-RUN pip install --no-cache-dir --upgrade pip && \
-    pip install --no-cache-dir -r requirements.txt
+# Using --verbose can sometimes give more insight into pip errors
+RUN echo "Starting pip install..." && \
+    pip install --no-cache-dir --upgrade pip && \
+    pip install --no-cache-dir --verbose -r requirements.txt && \
+    echo "Pip install completed."
 
 # Copy all files from the build context (app.py, etc.) into the working directory
 COPY . .
 
-# Create necessary directories that the app will use, as per user guidance
-# 'data' for persistent items (template, font, config)
-# 'downloads' for temporary raw images
-# 'session' for the Telethon session file
-RUN mkdir -p ./data ./downloads ./session && \
-    chmod -R 777 ./data ./downloads ./session
+# Create necessary directories that the app will use
+# These directories will be relative to WORKDIR (/app)
+RUN echo "Creating directories: ./data ./downloads ./session" && \
+    mkdir -p ./data ./downloads ./session && \
+    echo "Setting permissions for directories..." && \
+    chmod -R 777 ./data ./downloads ./session && \
+    echo "Permissions set."
+
+# List contents of /app for debugging (check build logs for this output)
+RUN echo "Contents of /app:" && ls -la /app
 
 # Command to run the application when the container launches
-CMD ["python", "app.py"]
+# The -u flag for python is equivalent to PYTHONUNBUFFERED=1
+CMD ["python", "-u", "app.py"]