fix: allowlist tests/ in gitleaks, add libopus for CI test job

- gitleaks flagged fake api_key in test fixtures as a secret leak;
  allowlist tests/ directory since it contains only mock data
- Install libopus0 in test runner for pymumble/opuslib import chain

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

.gitea/workflows/ci.yml

@@ -41,6 +41,7 @@ jobs:
       - uses: actions/setup-python@v5
         with:
           python-version: ${{ matrix.python-version }}
+      - run: sudo apt-get update && sudo apt-get install -y libopus0
       - run: pip install -e . && pip install pymumble pytest
       - run: pytest -v
 

.gitleaks.toml

@@ -0,0 +1,2 @@
+[allowlist]
+  paths = ["tests/"]