feat(web): cache dashboard aggregations with version invalidation

reaction_board/services/discovery.py

@@ -106,6 +106,8 @@ class DiscoveryService:
                     self._handle_item(item, channel, cfg, summary, pending, now)
 
         self._notify(pending, summary, now)
+        if summary.candidates or summary.notified:
+            self.repo.bump_cache_version("videos")
         summary.finished_at = self._now()
         self._log(
             "info" if not summary.errors else "warning",