Fix webhook avatar mismatch: pass avatar_url at send time

- Fixed missing client parameter in animated GIF webhook update path
- Added get_persona_avatar_urls() helper that returns bot's current Discord
  avatar URL for Miku persona (always fresh, no cache lag)
- Pass avatar_url on every webhook.send() call in bipolar_mode.py,
  persona_dialogue.py, and api.py so avatars always match current pfp
  regardless of webhook cache state

bot/api.py

@@ -1230,11 +1230,17 @@ async def manual_send_webhook(
                 for file_info in file_data:
                     discord_files.append(discord.File(io.BytesIO(file_info['content']), filename=file_info['filename']))
                 
-                # Send via webhook with display name
+                # Get current avatar URL for the persona
+                from utils.bipolar_mode import get_persona_avatar_urls
+                avatar_urls = get_persona_avatar_urls()
+                avatar_url = avatar_urls.get("evil_miku") if persona == "evil" else avatar_urls.get("miku")
+                
+                # Send via webhook with display name and current avatar
                 if discord_files:
                     await webhook.send(
                         content=message,
                         username=display_name,
+                        avatar_url=avatar_url,
                         files=discord_files,
                         wait=True
                     )
@@ -1242,6 +1248,7 @@ async def manual_send_webhook(
                     await webhook.send(
                         content=message,
                         username=display_name,
+                        avatar_url=avatar_url,
                         wait=True
                     )