ci(linux): add build workflow + Docker build instructions

docker/Dockerfile.source

@@ -0,0 +1,48 @@
+# Multi-stage build: clones rustdesk-server from a Git remote and builds the
+# hbbs / hbbr / rustdesk-utils binaries from source.
+#
+# Build args:
+#   RUSTDESK_GIT_URL    Git URL to clone (default: gitea.cstudio.ch fork)
+#   RUSTDESK_GIT_BRANCH Branch / tag / ref to check out (default: pro-features)
+#   RUST_VERSION        Rust toolchain image tag (default: 1-bookworm)
+
+ARG RUST_VERSION=1-bookworm
+
+FROM rust:${RUST_VERSION} AS builder
+
+ARG RUSTDESK_GIT_URL=https://gitea.cstudio.ch/mike/rustdesk-server.git
+ARG RUSTDESK_GIT_BRANCH=pro-features
+# sqlx::query! macros verify SQL at compile time against the checked-in
+# db_v2.sqlite3. Override only if you point cargo at a different DB.
+ARG DATABASE_URL=
+
+RUN apt-get update \
+ && apt-get install -y --no-install-recommends git ca-certificates pkg-config cmake \
+ && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /src
+
+RUN git clone --recurse-submodules --shallow-submodules \
+        --branch "${RUSTDESK_GIT_BRANCH}" --single-branch \
+        "${RUSTDESK_GIT_URL}" .
+
+RUN if [ -n "${DATABASE_URL}" ]; then export DATABASE_URL="${DATABASE_URL}"; fi \
+ && cargo build --release --bins
+
+# Runtime stage
+FROM debian:bookworm-slim
+
+RUN apt-get update \
+ && apt-get install -y --no-install-recommends ca-certificates tini \
+ && rm -rf /var/lib/apt/lists/*
+
+COPY --from=builder /src/target/release/hbbs           /usr/local/bin/hbbs
+COPY --from=builder /src/target/release/hbbr           /usr/local/bin/hbbr
+COPY --from=builder /src/target/release/rustdesk-utils /usr/local/bin/rustdesk-utils
+COPY --from=builder /src/admin_ui                       /opt/rustdesk/admin_ui
+
+WORKDIR /root
+EXPOSE 21114 21115 21116 21116/udp 21117 21118 21119
+
+ENTRYPOINT ["/usr/bin/tini", "--"]
+CMD ["hbbs"]