build(docker): Add Dockerfile

Dockerfile

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+# Dockerfile
+
+# ---- Planner Stage ----
+# Use the official Rust Alpine image as a base for planning.
+# We use the same base image for planner and builder for consistency.
+FROM rust:1-alpine AS planner
+WORKDIR /app
+# Install cargo-chef for build caching
+RUN apk add --no-cache musl-dev # Needed by chef
+RUN cargo install cargo-chef --locked
+COPY . .
+# Compute dependencies. This output will be cached if Cargo.toml/lock haven't changed.
+RUN cargo chef prepare --recipe-path recipe.json
+
+# ---- Builder Stage ----
+# Use the same Rust Alpine image for building.
+FROM rust:1-alpine AS builder
+WORKDIR /app
+# Install build dependencies for Alpine
+RUN apk add --no-cache build-base openssl-dev pkgconfig
+# Install cargo-chef again (could optimize but simpler this way)
+RUN cargo install cargo-chef --locked
+# Copy the dependency recipe from the planner stage
+COPY --from=planner /app/recipe.json recipe.json
+# Build dependencies based on the recipe. This layer is cached efficiently.
+RUN cargo chef cook --release --recipe-path recipe.json
+# Copy application code
+COPY . .
+# Build the application binary, linking against pre-built dependencies
+# Ensure the binary name matches your package name in Cargo.toml
+RUN cargo build --release --bin discord-music-bot-lavalink-rs
+
+# ---- Runtime Stage ----
+# Use a minimal Alpine image for the final runtime environment.
+FROM alpine:latest
+WORKDIR /app
+# Install runtime dependencies needed by the binary (e.g., SSL certs)
+RUN apk add --no-cache ca-certificates openssl
+# Copy the compiled application binary from the builder stage
+COPY --from=builder /app/target/release/discord-music-bot-lavalink-rs /app/
+# Set the binary as the entrypoint
+CMD ["./discord-music-bot-lavalink-rs"]