v3.2.1 — Fix relay issues: robust init, webhook fallback, debug command

Fixes:
- _init() now always sets _ready event even on error (prevents
  permanent relay blockage if init fails)
- Webhook method retries with cache refresh on stale/deleted webhooks
- Falls back to embed mode if webhooks fail (permissions, etc.)
- Empty content guard (prevents 400 errors on empty messages)
- Fixed deprecated discord.Embed.Empty usage for discord.py 2.x
- Prefix check now skips empty prefixes (prevents all-message block)
- asyncio.ensure_future() instead of bot.loop.create_task()
- Better error logging with exc_info for relay failures

New:
- [p]wh debug command — shows cog state, intents, permissions,
  webhook status, connected channels, and prefix diagnostics

wormhole/utils.py

@@ -261,8 +261,10 @@ def build_relay_embed(
 
     em = discord.Embed(description=message.content or "*[no text]*", colour=colour, timestamp=message.created_at)
     em.set_author(name=message.author.display_name, icon_url=message.author.display_avatar.url)
-    footer_icon = message.guild.icon.url if message.guild.icon else discord.Embed.Empty
-    em.set_footer(text=f"🌐 {guild_label} • #{message.channel.name}", icon_url=footer_icon)
+    if message.guild.icon:
+        em.set_footer(text=f"🌐 {guild_label} • #{message.channel.name}", icon_url=message.guild.icon.url)
+    else:
+        em.set_footer(text=f"🌐 {guild_label} • #{message.channel.name}")
 
     if message.attachments:
         img_set = False