fix: remove unused Loader2 import causing build failure

webapp/tipitaka-web/src/components/ai/AIPopup.tsx

@@ -1,7 +1,7 @@
 import React, { useState, useRef, useEffect, useCallback } from 'react';
 import { useAIStore } from '../../stores/aiStore';
 import { useReaderStore, useThemeStore } from '../../stores/appStore';
-import { X, Send, Sparkles, Trash2, Zap, Brain, Loader2 } from 'lucide-react';
+import { X, Send, Sparkles, Trash2, Zap, Brain } from 'lucide-react';
 import { motion } from 'framer-motion';
 
 const PANEL_STYLES: Record<string, { bg: string; text: string; border: string; msgBg: string }> = {