feat: implement Textual TUI and SQLite database for sensor management

tests/test_tui.py

@@ -0,0 +1,8 @@
+import pytest
+from sensorpajen.tui.app import SensorpajenApp
+
+def test_tui_app_init():
+    # Just test that we can instantiate it
+    app = SensorpajenApp()
+    assert app.discovery_manager is not None
+    assert app.sensor_config is not None