feat(packaging): nest protocol/ + ocf/ under smartthings_local, add PyPI packaging

Nest the two library packages under a single import namespace so they
can ship as one distribution:

  protocol/ -> smartthings_local/protocol/
  ocf/      -> smartthings_local/ocf/   (git mv, history preserved)

- Rewrite all imports protocol.* -> smartthings_local.protocol.*,
  ocf.* -> smartthings_local.ocf.* across the ocf modules, mqtt_demo/
  (bridge, descriptor, samples), and tests.
- Add pyproject.toml: dist name `smartthings-local`, hatch-vcs versioning
  from v* tags, wheel ships only smartthings_local/.
- Add .github/workflows/publish.yml: build + PyPI Trusted Publishing on
  v* tags (OIDC, no stored token).
- Force-include protocol/ocf_root_ca.pem via [tool.hatch.build] artifacts:
  it is tracked but matches .gitignore's *.pem, so hatchling's VCS file
  selection would drop it — and dtls_session.py loads it at runtime.
- Update mqtt_demo Dockerfile COPY and deploy.sh tar allowlist to the
  single smartthings_local/ package.
- .gitignore: build artifacts (_version.py, dist/, *.egg-info/).

Validated: pytest tests/ (11 passed), python -m build produces sdist +
wheel with the pem bundled, fresh pip install resolves all nested imports
with the pem readable from site-packages.

.github/workflows/publish.yml

@@ -0,0 +1,50 @@
+name: Publish to PyPI
+
+# Publishes smartthings-local to PyPI on a version tag (v1.2.3).
+# Uses PyPI Trusted Publishing (OIDC) — no API token is stored in the repo.
+# One-time setup on PyPI: add a trusted publisher for this repo pointing at
+# workflow `publish.yml` and environment `pypi`.
+
+on:
+  push:
+    tags:
+      - "v*"
+
+jobs:
+  build:
+    name: Build sdist + wheel
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0  # hatch-vcs needs full history + tags to derive the version
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.12"
+      - run: python -m pip install --upgrade build
+      - run: python -m build
+      - name: Verify the built version matches the tag
+        run: |
+          ls -l dist/
+          version="${GITHUB_REF_NAME#v}"
+          if ! ls dist/ | grep -q "smartthings_local-${version}"; then
+            echo "Built artifacts do not match tag version ${version}"; exit 1
+          fi
+      - uses: actions/upload-artifact@v4
+        with:
+          name: dist
+          path: dist/
+
+  publish:
+    name: Publish to PyPI
+    needs: build
+    runs-on: ubuntu-latest
+    environment: pypi
+    permissions:
+      id-token: write  # required for Trusted Publishing (OIDC)
+    steps:
+      - uses: actions/download-artifact@v4
+        with:
+          name: dist
+          path: dist/
+      - uses: pypa/gh-action-pypi-publish@release/v1