chore: set default speakers manually

app.py

@@ -235,8 +235,8 @@ async def main():
         speakers = []
         spaker2id = {}
 
-    main_speaker_name = None if len(speakers) == 0 else speakers[0]
-    supporter_speaker_name = None if len(speakers) < 2 else speakers[1]
+    main_speaker_name = "Anneli (テンション高め)"
+    supporter_speaker_name = "まい (ノーマル)"
 
     main_speaker_preview = None
     supporter_speaker_preview = None