Fix performance of home feed regeneration (#12084)

Fetching statuses from all followed accounts at once takes too long
within Postgres. Fetching them one by one and merging in Ruby
could be a lot less resource-intensive

Because the query for dynamically fetching the home timeline is so
heavy, we can no longer offer it when the home timeline is missing

app/javascript/mastodon/features/generic_not_found/index.js

@@ -4,7 +4,7 @@ import MissingIndicator from '../../components/missing_indicator';
 
 const GenericNotFound = () => (
   <Column>
-    <MissingIndicator />
+    <MissingIndicator fullPage />
   </Column>
 );