feat(web): cache dashboard aggregations with version invalidation

tools/import_fans_csv.py

@@ -202,6 +202,8 @@ def import_fans_series(
             ok=True,
             captured_at=_day_timestamp(date.fromisoformat(day)),
         )
+    if not dry_run and (inserted or updated or deleted):
+        repo.bump_cache_version("fans")
     return {
         "ok": True,
         "dry_run": bool(dry_run),