feat(ticket): rewrite ticket system from scratch inspired by Kuby

New minimal ticket system (dev only):
- Panel with create ticket button (Components V2, no accent colors)
- Category selection via dropdown or direct modal (1 cat)
- Ticket channel creation with permissions, staff role, welcome message
- Close flow: staff check, transcript HTML (dark theme), log, auto-delete
- /ticket setup, /ticket config (interactive panel)
- Storage: JSON per-ticket + config.json (singleton pattern)
- Modular architecture: data.py, storage.py, ui.py, transcript.py, cog.py
- Removed old modmail system

bot.py

@@ -26,7 +26,7 @@ class VisionBot(commands.Bot):
     async def setup_hook(self):
         logger.info("Chargement des cogs...")
         await self.load_extension("commandes.hello")
-        await self.load_extension("commandes.modmail")
+        await self.load_extension("tickets.cog")
 
         self.tree.on_error = self.on_app_command_error