Add DMR digital voice, WebSDR, and listening post enhancements

- DMR/P25 digital voice decoder mode with DSD-FME integration
- WebSDR mode with KiwiSDR audio proxy and websocket-client support
- Listening post waterfall/spectrogram visualization and audio streaming
- Dockerfile updates for mbelib and DSD-FME build dependencies
- New tests for DMR, WebSDR, KiwiSDR, waterfall, and signal guess API
- Chart.js date adapter for time-scale axes

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

tests/conftest.py

@@ -5,11 +5,13 @@ from app import app as flask_app
 from routes import register_blueprints
 
 
-@pytest.fixture
+@pytest.fixture(scope='session')
 def app():
     """Create application for testing."""
-    register_blueprints(flask_app)
     flask_app.config['TESTING'] = True
+    # Register blueprints only if not already registered
+    if 'pager' not in flask_app.blueprints:
+        register_blueprints(flask_app)
     return flask_app