Add OCI source label to link ghcr.io package to repository

This allows the GITHUB_TOKEN to push images in CI by linking the
container package to the repository.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: pike00

Dockerfile

@@ -24,6 +24,8 @@ RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 \
 # ── Stage 2: Runtime ────────────────────────────────────────────────
 FROM gcr.io/distroless/static-debian12:nonroot
 
+LABEL org.opencontainers.image.source="https://github.com/pike00/coldkey"
+
 COPY --from=builder /coldkey /coldkey
 COPY --from=builder /usr/share/zoneinfo /usr/share/zoneinfo