feat: add GHCR Docker workflow, update README with container registry instructions

- New .github/workflows/docker.yml publishes images to ghcr.io on tag push
- README Docker section now leads with 'docker pull' from GHCR
- docker-compose.yml defaults to GHCR image with build-from-source fallback
- Dockerfile: copy README.md for hatchling metadata resolution

.gitignore

@@ -81,3 +81,6 @@ frontend/src-tauri/binaries/ffmpeg
 # cuDNN 8 compat libs (auto-installed by scripts/setup_cudnn.py)
 cudnn8_compat/
 test-results/
+
+# Research repos (local only)
+research/