feat: docker packaging and readme

python:3.11-slim base relies on pip torch wheels bundling CUDA runtime libs,
with the host NVIDIA driver passed through via the nvidia container runtime
(compose GPU reservation); TORCH_HOME and XDG_CACHE_HOME point into the
mounted /data volume so Demucs/wav2vec2 weights survive container
recreation.

Docker was not installed in the implementation sandbox, so the image was
not built or run and remains untested. PyYAML was also unavailable, so
docker-compose.yml was not parse-checked programmatically — only hand
reviewed.

docker-compose.yml

@@ -0,0 +1,15 @@
+services:
+  karaoke-maker:
+    build: .
+    ports:
+      - "8000:8000"
+    volumes:
+      - ./config.toml:/config/config.toml:ro
+      - ./data:/data
+    deploy:
+      resources:
+        reservations:
+          devices:
+            - driver: nvidia
+              count: 1
+              capabilities: [gpu]