refactor: move docker files to /docker folder;

remove old buid workflow;

docker/Dockerfile

@@ -0,0 +1,23 @@
+FROM python:3.13-alpine
+
+WORKDIR /app
+
+# Copy application code (package) and bootstrap
+COPY yt-playlist-main.py /app/
+COPY src/ /app/
+COPY config/ /app/config/
+
+# Copy helper binaries from the build context (which includes extracted artifacts)
+COPY bin/ffmpeg /app/bin/ffmpeg
+COPY bin/yt-dlp /app/bin/yt-dlp
+COPY bin/aria2c /app/bin/aria2c
+
+# Copy entrypoint that maps environment variables to CLI flags
+COPY docker-entrypoint.sh /app/docker-entrypoint.sh
+RUN chmod +x /app/docker-entrypoint.sh && chmod +x /app/bin/* || true
+
+# Put the bundled bin directory first in PATH
+ENV PATH="/app/bin:${PATH}"
+
+ENTRYPOINT ["/app/docker-entrypoint.sh"]
+CMD [""]