Add Railway deploy files for web.yaak.app and the send proxy

Dockerfile.proxy

@@ -0,0 +1,18 @@
+# syntax=docker/dockerfile:1
+# The stateless send proxy for web.yaak.app. Builds only crates-server/yaak-send-proxy
+# (over yaak-http), so no plugins/Node. Binds a fixed 8080; Railway routes to it.
+
+FROM rust:1-bookworm AS build
+WORKDIR /app
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    pkg-config libssl-dev protobuf-compiler && rm -rf /var/lib/apt/lists/*
+COPY . .
+RUN cargo build --release -p yaak-send-proxy
+
+FROM debian:bookworm-slim
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    ca-certificates libssl3 && rm -rf /var/lib/apt/lists/*
+COPY --from=build /app/target/release/yaak-send-proxy /usr/local/bin/yaak-send-proxy
+ENV YAAK_PROXY_BIND=0.0.0.0:8080
+EXPOSE 8080
+CMD ["yaak-send-proxy"]