CodeBench: esikäännä Rust-riippuvuudet Docker-imageen — 35x nopeampi

Dummy-projekti samalla Cargo.toml:llä: cargo check + cargo build --tests
imageen. Runtime kääntyy vain itse projekti (~2.5s vs ~90s).

kipina-codebench/Dockerfile.cargo-test

@@ -1,4 +1,28 @@
 FROM rust:1.87-slim
 RUN apt-get update && apt-get install -y pkg-config libssl-dev && rm -rf /var/lib/apt/lists/*
 WORKDIR /work
+
+# Esikäännä riippuvuudet dummy-projektilla — nämä cachetaan Docker-layeriin
+RUN cargo init --name bench-precompile . && \
+    cat > Cargo.toml <<'TOML'
+[package]
+name = "bench-precompile"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+axum = "0.8"
+tokio = { version = "1", features = ["full"] }
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+sqlx = { version = "0.8", features = ["sqlite", "runtime-tokio"] }
+tower-http = { version = "0.6", features = ["cors"] }
+chrono = { version = "0.4", features = ["serde"] }
+
+[dev-dependencies]
+reqwest = { version = "0.12", default-features = false, features = ["json", "rustls-tls"] }
+tokio = { version = "1", features = ["full", "test-util"] }
+TOML
+RUN cargo check 2>&1 && cargo build --tests 2>&1 && rm -rf src target/debug/deps/bench_precompile* target/debug/bench-precompile*
+
 ENTRYPOINT ["sh", "-c", "cp -r /src/* . && cargo test 2>&1"]