Fix accounts search by full/partial display name and others (#11580)

- Restrict followers counts to local users to minimize local advantage
- Fix emoji shortcodes causing error in search
- Fix search syntax parse errors not being caught

app/lib/search_query_transformer.rb

@@ -75,6 +75,8 @@ class SearchQueryTransformer < Parslet::Transform
 
     if clause[:term]
       TermClause.new(prefix, operator, clause[:term].to_s)
+    elsif clause[:shortcode]
+      TermClause.new(prefix, operator, ":#{clause[:term]}:")
     elsif clause[:phrase]
       PhraseClause.new(prefix, operator, clause[:phrase].map { |p| p[:term].to_s }.join(' '))
     else