fix(jsons): add missing timeline import to broadcast.nim (#30)

formatUserAsJson is defined in timeline.nim but was not imported,
causing an undeclared identifier build error.

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: guanbinrui

src/jsons/broadcast.nim

@@ -5,7 +5,7 @@ import jester
 
 import ".."/routes/router_utils
 import ".."/[types, redis_cache]
-import list
+import list, timeline
 
 proc formatBroadcastAsJson*(bc: Broadcast): JsonNode =
   proc dateToUnix(dt: DateTime): int64 =