Add logviewer: web UI for the ClickHouse log store

Single Go binary with embedded Bootstrap 3 + jQuery UI, querying logs.raw
over the ClickHouse HTTP interface as the readonly logreader user. Runs
behind oauth2-proxy; the app does no auth itself. Server-side enforced
time bounds (15m default, 72h max), parameterized queries, raw-SQL WHERE
fragment wrapped with enforced bounds and LIMIT, tail polling with a
clamped cursor, facets, healthz. Woodpecker build/test plus tag-driven
image push to artifactapi docker-internal.

Dockerfile

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