Add scripts-to-rule-them-all scaffold (refs #1)

Add the standard STRTA scaffold, mirroring the conformant Go repos:

- script/ POSIX-sh entrypoints (bootstrap, setup, projectname, test,
  lint, fmt, fmt-check, check, docker, cibuild, precommit,
  install-precommit).
- Makefile rewritten as thin shims: .PHONY plus the nine standard
  targets each delegating to script/NAME; repo-specific build, clean,
  and try targets retained.
- .golangci.yml matching the org-standard Go lint config.
- Dockerfile whose build runs make check then make build, so the image
  fails on any check failure.
- .gitea/workflows/check.yml running script/cibuild.

make fmt-check and make test are green. make check is not yet green
because of pre-existing lint findings in the application code, which
are out of scope for this scaffold change; hence refs (not closes).

Dockerfile

@@ -0,0 +1,34 @@
+# Build stage
+# golang 1.25-alpine, 2026-02-28
+FROM golang@sha256:f6751d823c26342f9506c03797d2527668d095b0a15f1862cddb4d927a7a4ced AS builder
+
+RUN apk add --no-cache git make gcc musl-dev binutils-gold
+
+# golangci-lint v2.10.1
+RUN go install github.com/golangci/golangci-lint/v2/cmd/golangci-lint@5d1e709b7be35cb2025444e19de266b056b7b7ee
+# goimports v0.42.0
+RUN go install golang.org/x/tools/cmd/goimports@009367f5c17a8d4c45a961a3a509277190a9a6f0
+
+WORKDIR /src
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+
+# Run all checks - build fails if any check fails
+RUN make check
+
+# Build the binary
+RUN make build
+
+# Runtime stage
+# alpine 3.21, 2026-02-28
+FROM alpine@sha256:c3f8e73fdb79deaebaa2037150150191b9dcbfba68b4a46d70103204c53f4709
+
+RUN apk add --no-cache ca-certificates tzdata
+
+WORKDIR /app
+
+COPY --from=builder /src/attrsum /app/attrsum
+
+ENTRYPOINT ["/app/attrsum"]