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/integration/test_int_boot_diagnosis.py

@@ -0,0 +1,57 @@
+import sys
+import os
+
+# Add project root to path
+sys.path.append(os.getcwd())
+
+print("--- Starting Import Diagnosis ---")
+
+try:
+    print("1. Importing app.config...")
+    from app import config
+    print(f"   Success. Settings found: {hasattr(config, 'settings')}")
+except Exception as e:
+    print(f"   FAILED: {e}")
+    sys.exit(1)
+
+try:
+    print("2. Importing app.log...")
+    import app.log
+    print("   Success.")
+except Exception as e:
+    print(f"   FAILED: {e}")
+    import traceback
+    traceback.print_exc()
+    sys.exit(1)
+
+try:
+    print("3. Importing app.db_connection...")
+    import app.db_connection
+    print("   Success.")
+except Exception as e:
+    print(f"   FAILED: {e}")
+    import traceback
+    traceback.print_exc()
+    sys.exit(1)
+
+try:
+    print("4. Importing app.db_sql...")
+    import app.db_sql
+    print("   Success.")
+except Exception as e:
+    print(f"   FAILED: {e}")
+    import traceback
+    traceback.print_exc()
+    sys.exit(1)
+
+try:
+    print("5. Importing app.main...")
+    import app.main
+    print("   Success.")
+except Exception as e:
+    print(f"   FAILED: {e}")
+    import traceback
+    traceback.print_exc()
+    sys.exit(1)
+
+print("--- Diagnosis Complete: No top-level import errors found in local env ---")