Add Dockerfile and docker-compose

[aviralgarg05]

Add Docker support for easy deployment and development:

1. Create Dockerfile for production builds (multi-stage, minimal image)
2. Create docker-compose.yml for local development
3. Add volume mounts for data persistence
4. Document Docker usage in README
5. Add CI job to build and push Docker image on release

FROM rust:1.75 AS builder
WORKDIR /app
COPY . .
RUN cargo build --release

FROM debian:bookworm-slim
COPY --from=builder /app/target/release/nexum /usr/local/bin/
CMD ["nexum"]

[ignorant05]

Hey, can i do this task ? if so, just assign me.

[aviralgarg05]

Go for it! Let me know here if you face any issues