fix(gateway): update paths in Dockerfile for gateway source

Signed-off-by: Klagarge <remi@heredero.ch>

gateway/Dockerfile

@@ -2,10 +2,10 @@ FROM golang:1.23-alpine AS builder
 
 WORKDIR /app
 
-COPY ./src/go.mod ./src/go.sum ./
+COPY ./gateway/src/go.mod ./gateway/src/go.sum ./
 RUN go mod tidy
 
-COPY ./src .
+COPY ./gateway/src .
 #RUN CGO_ENABLED=0 go build -ldflags="-w -s" -o /gateway .
 RUN go build -o /gateway .