build: switch to pre-built python-ffmpeg docker image

The new base image already includes ffmpeg and flask, simplifying our Dockerfile and reducing build time

Author: painteau

CHANGELOG.md

@@ -15,7 +15,7 @@ The format is inspired by [Keep a Changelog](https://keepachangelog.com/en/1.1.0
 
 ### Changed
 
-- Base Docker image updated to `python:3.14-slim`.
+- Base Docker image updated to `ghcr.io/painteau/python-ffmpeg:latest` (optimized with pre-installed ffmpeg/flask).
 - Shortcode extraction improved to support more Instagram URL formats.
 - Error handling with Instaloader refined with appropriate HTTP status codes (404, 403, 429, 503, 502).
 

Dockerfile

@@ -1,11 +1,8 @@
-FROM python:3.14-slim
+FROM ghcr.io/painteau/python-ffmpeg:latest
 ENV PYTHONUNBUFFERED=1
 
 WORKDIR /app
-RUN apt-get update \
-    && apt-get install -y --no-install-recommends ffmpeg \
-    && pip install instaloader flask gunicorn \
-    && rm -rf /var/lib/apt/lists/*
+RUN pip install instaloader
 
 COPY app.py .