Fix 406 error in MCP tool execution - add Accept header

The /mcp/call_tool endpoint was returning 406 "Not Acceptable" error
because the request didn't include an Accept header.

Fixed by adding "Accept": "application/json" to the request headers.

Error message was:
"Not Acceptable: Client must accept application/json"

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

scripts/discordbot.py

@@ -88,7 +88,8 @@ async def execute_mcp_tool(tool_name: str, arguments: dict) -> str:
         base_url = LITELLM_API_BASE.rstrip('/')
         headers = {
             "Authorization": f"Bearer {LITELLM_API_KEY}",
-            "Content-Type": "application/json"
+            "Content-Type": "application/json",
+            "Accept": "application/json"
         }
 
         debug_log(f"Executing MCP tool: {tool_name} with args: {arguments}")