feat: ship Rust login manager and GitLab release pipeline

Replace the legacy Go implementation as the production path, quarantine the reference tree, add deterministic release packaging and version metadata, and run verification through GitLab CI.

Dockerfile.test

@@ -0,0 +1,20 @@
+FROM rust:1.88.0-bookworm
+
+ENV CARGO_TERM_COLOR=never
+ENV RUST_BACKTRACE=1
+
+RUN apt-get update \
+    && apt-get install --no-install-recommends -y \
+        libpam0g-dev libpam-modules xauth xvfb pkg-config \
+    && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /workspace
+COPY Cargo.toml Cargo.lock rust-toolchain.toml ./
+COPY build.rs ./
+COPY rust ./rust
+COPY crates ./crates
+
+RUN cargo fmt --all -- --check \
+    && cargo test --locked --all-targets \
+    && cargo clippy --locked --all-targets --all-features -- -D warnings \
+    && RUSTDOCFLAGS="-D warnings" cargo doc --locked --no-deps