feat(docker): Add API Gateway Dockerfile

cmd/api-gateway/Dockerfile

@@ -0,0 +1,36 @@
+# Build stage
+FROM golang:1.25-alpine AS builder
+
+WORKDIR /build
+
+# Install build dependencies
+RUN apk add --no-cache git make
+
+# Copy go mod files
+COPY go.mod go.sum ./
+RUN go mod download
+
+# Copy source code
+COPY . .
+
+# Build the service
+WORKDIR /build/cmd/api-gateway
+RUN CGO_ENABLED=0 GOOS=linux go build -o api-gateway -a -installsuffix cgo .
+
+# Runtime stage
+FROM alpine:latest
+
+RUN apk --no-cache add ca-certificates tzdata
+
+WORKDIR /app
+
+# Copy binary from builder
+COPY --from=builder /build/cmd/api-gateway/api-gateway .
+
+# Copy config files
+COPY --from=builder /build/config ./config
+
+EXPOSE 8080
+
+CMD ["./api-gateway"]
+