Add scheduled refresh for tables that change at a fixed time of day

src/sqlmem/stats.py

@@ -9,7 +9,7 @@ class TableState:
     LOADING = "loading"        # a full load is in progress
     REFRESHING = "refreshing"  # an incremental (delta) refresh is in progress
     READY = "ready"            # cached and idle
-    STALE = "stale"            # TTL expired — will reload on next access
+    STALE = "stale"            # TTL expired / schedule slot passed — reloads on next access
     ERROR = "error"            # the last load failed
 
 
@@ -25,7 +25,7 @@ class TableStats:
     # the first cycle runs after start. Answers "is the refresh loop alive?".
     last_refresh: str | None = None
     state: str = TableState.READY
-    tracking: str = "static"  # "delta" | "ttl" | "static"
+    tracking: str = "static"  # "delta" | "ttl" | "schedule" | "static"
     # Most recent load/refresh failure for this table, if any. ``consecutive_failures``
     # resets to 0 on the next success, so > 0 means the table is currently failing.
     last_error: str | None = None