refactor: rebrand from cs-agent to BossChat

- Rename Go module: cs-agent → bosschat
- Rename all import paths across 200+ Go files
- Rename SDK: cs-ai-agent-sdk → bosschat-sdk
- Rename message protocol: cs-agent:* → bosschat:*
- Rename JS globals: CSAgentConfig → BossChatConfig
- Rename CSS classes: cs-agent-* → bosschat-*
- Update Makefile APP_NAME and ARCHIVE_NAME
- Update logo assets
- Fix display name: BoosChat → BossChat

web/components/kefu/message-list.tsx

@@ -214,7 +214,7 @@ export const KefuMessageList = forwardRef<KefuMessageListHandle, KefuMessageList
     return (
       <div
         ref={containerRef}
-        className="cs-agent-scrollbar flex min-h-0 flex-1 flex-col gap-4 overflow-y-auto px-4 py-4"
+        className="bosschat-scrollbar flex min-h-0 flex-1 flex-col gap-4 overflow-y-auto px-4 py-4"
       >
         <div ref={contentRef} className="flex flex-col gap-4">
           {hasMoreOlder && onLoadOlder ? (