Wire datetime_columns through query params and reads; add db_size and vacuum guard

src/sqlmem/engine.py

@@ -67,6 +67,7 @@ class CachingEngine:
         dialect: str | None = None,
         pragmas: dict[str, str | int] | None = None,
         datetime_columns: dict[str, list[str]] | None = None,
+        return_datetime: bool = True,
         blocking_startup_refresh: bool = False,
     ) -> None:
         self._source_engine = source_engine
@@ -83,6 +84,7 @@ class CachingEngine:
             fetch_batch=fetch_batch if fetch_batch is not None else FETCH_BATCH_SIZE,
             pragmas=pragmas,
             datetime_columns=datetime_columns,
+            return_datetime=return_datetime,
         )
         self._registry = ColumnRegistry(self._cache.connection)
         self._stats = StatsCollector()
@@ -152,7 +154,11 @@ class CachingEngine:
         last_runs = self._cache.get_last_runs()
         with self._cache._lock:
             base = self._stats.snapshot(self._cache.connection, states)
-        base = replace(base, errors=self._cache.error_total)
+        base = replace(
+            base,
+            errors=self._cache.error_total,
+            db_size_bytes=self._cache.db_size_bytes(),
+        )
         return replace(
             base,
             tables={n: self._enrich(n, t, errors, last_runs) for n, t in base.tables.items()},