control-plane: use btree index for log_lines

Replaces the current BRIN index on the `internal.log_lines` table with a btree
index.  The BRIN index would require queries to use the `logged_at` timestamp
in the where clause in order for it to be effective.  Neither the UI or flowctl
do that currently. The btree index works well when only filtering on token, so
this changes to just using that.

supabase/migrations/30_log_lines_index.sql

@@ -0,0 +1,11 @@
+
+-- The previous BRIN index on internal.log_lines is ineffective for queries that don't 
+-- supply a where condition on the `logged_at` timestamp. Currently, that represents
+-- all queries against that table. This drops the old BRIN index in favor of a regular
+-- btree index, which is effective when queries only provide the `token`.
+
+begin;
+create index idx_logs_token on internal.log_lines (token);
+drop index internal.idx_logs_token_logged_at;
+commit;
+