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/archive/check_db_schema.py

@@ -0,0 +1,13 @@
+from app.db_sql import db
+from sqlalchemy import text
+
+def check_columns():
+    try:
+        result = db.execute(text("DESCRIBE account"))
+        columns = [row[0] for row in result.fetchall()]
+        print(f"Columns in 'account': {columns}")
+    except Exception as e:
+        print(f"Error describing 'account': {e}")
+
+if __name__ == "__main__":
+    check_columns()