feat: add Dockerfile and build script for multi-stage Docker builds

Dockerfile

@@ -0,0 +1,32 @@
+# ---------- Builder Stage ----------
+FROM golang:1.24.2 AS builder
+ARG GIT_AUTH_TOKEN
+RUN git config --global url."https://${GIT_AUTH_TOKEN}:x-oauth-basic@git.denco.store/".insteadOf "https://git.denco.store/"
+
+WORKDIR /app
+
+# copy only go.mod and go.sum first
+COPY go.mod go.sum ./
+RUN go mod download
+
+# now copy the rest of the code
+COPY . .
+
+# build binaries
+RUN CGO_ENABLED=0 GOOS=linux go build -o server ./cmd/server/main.go \
+ && CGO_ENABLED=0 GOOS=linux go build -o tasks_server ./cmd/tasks_server/main.go
+
+
+
+# ---------- Final Image: Server ----------
+FROM gcr.io/distroless/static-debian12 AS server
+WORKDIR /app
+COPY --from=builder /app/server .
+ENTRYPOINT ["./server"]
+
+
+# ---------- Final Image: Tasks Server ----------
+FROM gcr.io/distroless/static-debian12 AS tasks_server
+WORKDIR /app
+COPY --from=builder /app/tasks_server .
+ENTRYPOINT ["./tasks_server"]