fix: update Dockerfile to use Python 3.10 and improve comments

Dockerfile

@@ -1,25 +1,29 @@
-# Use lightweight Python image
-FROM python:3.11-slim
+# Use an official Python runtime as a parent image
+FROM python:3.10-slim-buster
 
-# Install ffmpeg (needed by yt-dlp)
-RUN apt-get update && apt-get install -y \
-    ffmpeg \
-    && rm -rf /var/lib/apt/lists/*
+# 1. Install FFmpeg
+# Debian/Ubuntu based images allow easy installation via apt
+# ffmpeg is essential for the conversion process
+RUN apt-get update && \
+    apt-get install -y ffmpeg && \
+    rm -rf /var/lib/apt/lists/*
 
-# Set working directory
+# Set the working directory in the container
 WORKDIR /app
 
-# Copy requirements first
-COPY requirements.txt .
+# 2. Copy requirements file and install dependencies
+COPY requirements.txt /app/requirements.txt
 
-# Install dependencies
+# Install Python dependencies, including Gunicorn for production server
 RUN pip install --no-cache-dir -r requirements.txt
 
-# Copy project files
-COPY . .
+# 3. Copy the application code
+COPY ffmpeg_service.py /app/
 
-# Expose port for Render
-EXPOSE 8080
+# Port 8080 is the standard port for Hugging Face Spaces (hardcoded in CMD)
+EXPOSE 5001
 
-# Start Flask app directly
-CMD ["python", "app.py"]
+# 4. Run the Flask application using Gunicorn
+# Binds to 0.0.0.0:8080 as required by HF Spaces
+# Format: 'module_name:app_variable_name' -> 'ffmpeg_service:ffmpeg_app'
+CMD exec gunicorn --bind 0.0.0.0:5001 --workers 2 ffmpeg_service:ffmpeg_app