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/unit/test_unit_errors.py

@@ -0,0 +1,44 @@
+import sys
+import os
+import asyncio
+from unittest.mock import MagicMock, AsyncMock
+
+# --- Environment Setup ---
+sys.modules['redis'] = MagicMock()
+sys.modules['sqlalchemy'] = MagicMock()
+sys.modules['sqlalchemy.text'] = MagicMock()
+sys.modules['app.config'] = MagicMock()
+sys.modules['app.log'] = MagicMock()
+sys.modules['app.lib_general'] = MagicMock()
+
+# Mock app.db_sql
+mock_db_sql = MagicMock()
+mock_db_sql.get_last_sql_error.return_value = '(pymysql.err.IntegrityError) (1062, "Duplicate entry \'test-id\' for key \'id_random\'" )'
+sys.modules['app.db_sql'] = mock_db_sql
+
+# Add project root to path
+sys.path.append(os.getcwd())
+
+from app.lib_api_crud_v3 import format_db_error
+
+def test_error_formatting():
+    print("\n--- Testing Error Formatting ---")
+    raw = '(pymysql.err.IntegrityError) (1062, "Duplicate entry \'abc\' for key \'id_random\'" )'
+    formatted = format_db_error(raw)
+    print(f"Raw: {raw}")
+    print(f"Formatted: {formatted}")
+    if formatted == "Duplicate entry 'abc' for key 'id_random'":
+        print("✅ Error formatting works.")
+    else:
+        print("❌ Error formatting FAILED.")
+
+def test_null_error_handling():
+    print("\n--- Testing Null Error Handling ---")
+    if format_db_error(None) == "":
+        print("✅ Null error handled correctly.")
+    else:
+        print("❌ Null error check FAILED.")
+
+if __name__ == "__main__":
+    test_error_formatting()
+    test_null_error_handling()