updated files for a prod env

backend/Dockerfile.prod

@@ -0,0 +1,26 @@
+# ---- build ----
+FROM golang:1.24 AS build
+WORKDIR /src
+COPY go.mod go.sum ./
+RUN go mod download
+COPY . .
+RUN CGO_ENABLED=0 GOOS=linux go build -trimpath -ldflags="-s -w" -o /out/vindn-backend ./cmd/server
+
+# ---- runtime ----
+# "static" (not "-nonroot") to match the existing root:root ownership of the
+# bind-mounted ./backend/public/storage host directory shared with the
+# frontend container — switching to a non-root UID here would need that
+# directory rechowned too, or every media download starts failing silently.
+FROM gcr.io/distroless/static-debian12
+
+# The imported event data and the site's audience are both German-local;
+# default to that instead of UTC so the twice-daily cron (see tasks/Cronjob.go)
+# actually fires at 06:00/18:00 German time, not UTC. distroless/static ships
+# tzdata, but time/tzdata is also embedded in the binary above for safety.
+ENV TZ=Europe/Berlin
+
+WORKDIR /app
+COPY --from=build /out/vindn-backend ./vindn-backend
+
+EXPOSE 8080
+ENTRYPOINT ["./vindn-backend"]