fix: convert binary UUID to text in activity feed sync query

Fixes Jason.EncodeError when rendering activity feed. PostgreSQL
array_agg was returning binary UUID which caused invalid UTF-8 bytes
when interpolated into 'sy-#{row.id}' string. Cast to ::text in the
fragment to ensure string representation.

lib/towerops/activity_feed.ex

@@ -301,7 +301,7 @@ defmodule Towerops.ActivityFeed do
       from(sl in SyncLog,
         where: sl.organization_id == ^org_id,
         select: %{
-          id: fragment("(array_agg(? ORDER BY ? DESC))[1]", sl.id, sl.inserted_at),
+          id: fragment("(array_agg(?::text ORDER BY ? DESC))[1]", sl.id, sl.inserted_at),
           timestamp: fragment("date_trunc('minute', ?)", sl.inserted_at),
           status: fragment("(array_agg(? ORDER BY ? DESC))[1]", sl.status, sl.inserted_at),
           records_synced: sum(sl.records_synced),