feat(stats): add migration v7 visit table and client-ip helpers

tests/test_web_queries.py

@@ -459,7 +459,7 @@ def test_about_payload():
             assert about["snapshot_days"] == 3
             assert about["snapshot_first_date"] == DATES[0]
             assert about["fans_start_date"] == DATES[0]
-            assert about["schema_version"] == 6
+            assert about["schema_version"] == 7
             assert about["analytics"] == {
                 "min_duration_seconds": 600,
                 "maturity_days": 2,