waitfordb: initial tool — env-configured wait-for-DB init container

Small Go tool + distroless container used as a K8s initContainer to block an
app until its database (Postgres/MySQL) is reachable. Env-var configured
(WAITFORDB_* + libpq PG* fallback), configurable timeout/interval, redacted
logs, exit codes. Woodpecker CI publishes docker-internal/waitfordb on tag.

Dockerfile

@@ -0,0 +1,18 @@
+FROM golang:1.25-alpine AS builder
+
+WORKDIR /build
+
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+
+ARG VERSION=dev
+RUN CGO_ENABLED=0 go build -ldflags="-s -w -X main.version=${VERSION}" -o waitfordb .
+
+# distroless static ships ca-certificates and runs as an unprivileged user.
+FROM gcr.io/distroless/static-debian12:nonroot
+
+COPY --from=builder /build/waitfordb /usr/local/bin/waitfordb
+
+ENTRYPOINT ["waitfordb"]