fix(ci): add keepkeylib to PYTHONPATH for bare protobuf imports

Generated protobuf files (messages_pb2.py) use bare imports like
`import types_pb2` instead of relative imports. This works inside
the firmware Docker container where keepkeylib/ is on sys.path
directly, but fails with pip install -e. Adding keepkeylib/ to
PYTHONPATH resolves the import chain.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: BitHighlander

.github/workflows/ci.yml

@@ -91,6 +91,7 @@ jobs:
         env:
           KK_TRANSPORT_MAIN: "127.0.0.1:11044"
           KK_TRANSPORT_DEBUG: "127.0.0.1:11045"
+          PYTHONPATH: "${{ github.workspace }}/keepkeylib:${{ github.workspace }}"
         run: |
           cd tests
           pytest -v --junitxml=junit.xml 2>&1 | tee pytest-output.txt