feat: usos sign-in, private calendar feed and timetable archive

Dockerfile

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+FROM golang:1.27-alpine@sha256:4cb7ac979db5fcc41cae44b2227ba5ab8a51e8807f40d9ba4dee20a0ad960b5b AS build
+
+WORKDIR /src
+
+ENV CGO_ENABLED=0
+
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY cmd ./cmd
+COPY internal ./internal
+
+RUN go build -trimpath -ldflags "-s -w" -o /out/usoscal ./cmd/usoscal
+
+FROM alpine:3.24@sha256:294b683cb724975bec92580e1e685676bd4b50bda910ddb8c51d4cabeaec77e6
+
+WORKDIR /app
+
+COPY --from=build /out/usoscal /usr/local/bin/usoscal
+
+CMD ["usoscal"]