Tests: Reorganize test suite into functional subdirectories

- Categorized scripts into tests/unit/, tests/integration/, tests/e2e/, and tests/tools/.
- Adopted consistent naming prefixes (test_unit_*, test_int_*, test_e2e_*, tool_*).
- Renamed conftest_mock.py to mock_config_helper.py for clarity.
- Updated test_int_boot_diagnosis.py with sys.path setup for root-level execution.

tests/mock_config_helper.py

@@ -0,0 +1,10 @@
+import sys
+from unittest.mock import MagicMock
+
+# Create a mock for app.config before any other app imports
+mock_config = MagicMock()
+mock_config.settings = MagicMock()
+
+# Manually inject into sys.modules
+sys.modules["app.config"] = mock_config
+print("MOCKED: app.config")