Merge news and email search results

server/sql/threads.sql

@@ -1,4 +1,5 @@
 SELECT
+    site,
     date,
     is_read,
     title,
@@ -8,7 +9,7 @@ FROM
     post p
     JOIN feed f ON p.site = f.slug
 WHERE
-    site = $1
+    ($1::text IS NULL OR site = $1)
     AND (
         NOT $2
         OR NOT is_read