Add Dockerfile and docker-compose for containerised deploys

Multi-stage build: rust:1-slim-bookworm to compile (needs a recent
toolchain per smarm/urus's MSRV), then a distroless/cc runtime image
since the binary only links against glibc/libgcc/libm (checked via
ldd) - no shell or package manager needed at runtime, ~27MB vs ~87MB
for a debian-slim runtime.

- CCC_DB_PATH defaults to /data/cdn.db in-container
- docker-compose.yml persists /data in a named volume, maps 8333

Dockerfile

@@ -0,0 +1,24 @@
+# --- build stage ---
+FROM rust:1-slim-bookworm AS builder
+WORKDIR /build
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    build-essential pkg-config ca-certificates git \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY . .
+RUN cargo build --release
+
+# --- runtime stage ---
+# distroless/cc: just glibc + libgcc + libm, no shell/package manager.
+# Matches what `ldd target/release/CCC` reports we actually need.
+FROM gcr.io/distroless/cc-debian12
+WORKDIR /data
+
+COPY --from=builder /build/target/release/CCC /usr/local/bin/ccc
+
+ENV CCC_DB_PATH=/data/cdn.db
+EXPOSE 8333
+
+ENTRYPOINT ["/usr/local/bin/ccc"]
+CMD ["serve", "--port", "8333"]