fix: restore Bazel proto_library rules broken by Bzlmod migration

[fcostaoliveira]

Summary

After a dormant period, CI began failing on both build-and-test and test-deb-build jobs with:

ERROR: name 'proto_library' is not defined
ERROR: name 'cc_proto_library' is not defined
ERROR: package contains errors: src/quipper

Root cause: Under Bzlmod, proto_library and cc_proto_library are no longer globally available as native rules. They must be explicitly loaded from the @protobuf module (protobuf 21+/Bzlmod requirement). Both src/quipper/BUILD and src/BUILD were using these rules without the required load(...) statements.

Changes

Added the following two load statements at the top of both src/quipper/BUILD and src/BUILD:

load("@protobuf//bazel:proto_library.bzl", "proto_library")
load("@protobuf//bazel:cc_proto_library.bzl", "cc_proto_library")

The MODULE.bazel already correctly declares protobuf as a bazel_dep (version 31.1) — no changes needed there. Only the BUILD file load statements were missing.

Test plan

• build-and-test CI job passes (bazel build + test on //src:all //src/quipper:all)
• test-deb-build CI job passes (the deb build script calls bazel under the hood)

[fcostaoliveira]

Superseded by #13 which includes the complete fix: rules_proto, rules_cc, and .bazelversion pinned to Bazel 8.0.0.