feat: homework multi-image upload and crop

backend/Dockerfile

@@ -0,0 +1,21 @@
+FROM golang:1.22-alpine AS build
+
+RUN apk add --no-cache gcc musl-dev
+
+WORKDIR /app
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+RUN CGO_ENABLED=1 GOOS=linux go build -o /bin/homework-backend ./
+
+FROM alpine:3.20
+RUN apk add --no-cache ca-certificates
+
+WORKDIR /app
+ENV DB_PATH=/data/homework.db
+
+COPY --from=build /bin/homework-backend /app/server
+EXPOSE 8080
+
+CMD ["/app/server"]