ci: add notify-failure, pytest with coverage, and 49 unit tests

- lint.yml: add notify-failure Matrix alert job
- test.yml: new workflow running pytest with pytest-cov for coverage
- .coveragerc: omit tests and site-packages from coverage
- .gitignore: ignore __pycache__ and .pyc files
- tests/test_hwmon.py: 49 unit tests covering SystemHealthMonitor
  (temperature parsing, service monitoring, disk usage, metric collection,
  dry run behaviour); uses unittest.mock to isolate from env/filesystem

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

.gitea/workflows/lint.yml

@@ -21,3 +21,21 @@ jobs:
 
       - name: Run flake8
         run: flake8 . --exclude=__pycache__,.git
+
+  notify-failure:
+    name: Notify on failure
+    runs-on: ubuntu-latest
+    needs: [python-lint]
+    if: failure() && github.event_name == 'push'
+    steps:
+      - name: Send Matrix alert
+        env:
+          MATRIX_WEBHOOK_URL: ${{ secrets.MATRIX_WEBHOOK_URL }}
+          REPO: ${{ github.repository }}
+          BRANCH: ${{ github.ref_name }}
+          RUN_URL: ${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}
+        run: |
+          if [ -z "$MATRIX_WEBHOOK_URL" ] || [ "$MATRIX_WEBHOOK_URL" = "CONFIGURE_ME" ]; then exit 0; fi
+          curl -sf -X POST "$MATRIX_WEBHOOK_URL" \
+            -H "Content-Type: application/json" \
+            -d "{\"text\":\"CI FAILED: ${REPO} @ ${BRANCH} — ${RUN_URL}\"}"