ssb: Add a lookup table of max sequence and timestamp per account.f

apps/ssb/tf-app.js

@@ -402,10 +402,9 @@ class TfElement extends LitElement {
 	async fetch_user_info(users) {
 		let info = await tfrpc.rpc.query(
 			`
-				SELECT messages.author, MAX(messages.sequence) AS max_seq, MAX(timestamp) AS max_ts FROM messages
+				SELECT messages_stats.author, messages_stats.max_sequence, messages_stats.max_timestamp AS max_ts FROM messages_stats
 				JOIN json_each(?) AS following
-				ON messages.author = following.value
-				GROUP BY messages.author
+				ON messages_stats.author = following.value
 			`,
 			[JSON.stringify(Object.keys(users))]
 		);