feat: update dockerfiles and add .dockerignore

backend/.dockerignore

@@ -0,0 +1,6 @@
+.git
+docker-compose.yml
+data/
+Makefile
+.env
+docs/

backend/Dockerfile

@@ -3,18 +3,21 @@ FROM golang:1.25.6 AS builder
 
 WORKDIR /app
 
-COPY  . .
 ENV CGO_ENABLED=0
 ENV GIN_MODE=release
-RUN go mod tidy
+
+COPY  go.mod go.sum ./
+RUN go mod download
+
+COPY . .
 RUN go build -ldflags "-s -w" -o backend ./cmd/main.go
 
 
 FROM alpine:3.23.0
-
+RUN adduser -D appuser && apk add --no-cache curl
 COPY --from=builder /app/backend .
-
+RUN chown appuser:appuser ./backend
+USER appuser
 EXPOSE 8080
-RUN apk add --no-cache curl
 HEALTHCHECK CMD curl --fail http://localhost:8080/health || exit 1
 CMD ["./backend"]