fix: pass RAILWAY_GIT_COMMIT_SHA through Docker, provide Cargo.toml for frontend (version retrieval)

Dockerfile

@@ -1,5 +1,6 @@
 # Build arguments
 ARG RUST_VERSION=1.89.0
+ARG RAILWAY_GIT_COMMIT_SHA
 
 # Frontend Build Stage
 FROM node:22-bookworm-slim AS frontend-builder
@@ -9,6 +10,9 @@ RUN npm install -g pnpm
 
 WORKDIR /app
 
+# Copy backend Cargo.toml for build-time version retrieval
+COPY ./Cargo.toml ./
+
 # Copy frontend package files
 COPY ./web/package.json ./web/pnpm-lock.yaml ./
 
@@ -24,6 +28,9 @@ RUN pnpm run build
 # Rust Build Stage
 FROM rust:${RUST_VERSION}-bookworm AS builder
 
+# Set build-time environment variable for Railway Git commit SHA
+ENV RAILWAY_GIT_COMMIT_SHA=${RAILWAY_GIT_COMMIT_SHA}
+
 # Install build dependencies
 RUN apt-get update && apt-get install -y \
     pkg-config \