tests: centralize script path setup in conftest.py

Add a pytest-discovered tests/conftest.py for the last30days scripts path and
remove duplicate per-file sys.path.insert boilerplate from tests.

Normalize affected imports to rely on the shared scripts path and remove the
now-unneeded E402 suppressions.

tests/test_setup_wizard.py

@@ -1,17 +1,11 @@
 """Tests for the first-run setup wizard module."""
 
-import os
-import sys
 import tempfile
 from pathlib import Path
 from unittest.mock import patch, MagicMock
 
 import pytest
 
-# Add scripts dir to path
-SCRIPTS_DIR = Path(__file__).parent.parent / "skills" / "last30days" / "scripts"
-sys.path.insert(0, str(SCRIPTS_DIR))
-
 from lib import setup_wizard