feat: GuiPresence (chat-service presence backend, gateway route, mod module); restore TODO history

backend/chat-service/Dockerfile

@@ -0,0 +1,20 @@
+# Build context must be backend/ (the workspace root).
+FROM rust:1-trixie AS builder
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    protobuf-compiler pkg-config libssl-dev ca-certificates \
+    && rm -rf /var/lib/apt/lists/*
+WORKDIR /build
+COPY Cargo.toml Cargo.lock ./
+COPY common ./common
+COPY accounts-service ./accounts-service
+COPY gateway ./gateway
+COPY configs-service ./configs-service
+COPY chat-service ./chat-service
+RUN cargo build --release -p chat-service
+
+FROM debian:trixie-slim
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    ca-certificates libssl3 \
+    && rm -rf /var/lib/apt/lists/*
+COPY --from=builder /build/target/release/chat-service /usr/local/bin/chat-service
+ENTRYPOINT ["/usr/local/bin/chat-service"]