fix(icons): replace lucide-react with @mui/icons-material

Replace lucide-react icon imports with @mui/icons-material equivalents
across all timetable pages and common Modal component.

Icons replaced:
- lucide-react Check, X, UserPlus, Users, Filter, Search -> MUI equivalents
- lucide-react ChevronDown, ChevronLeft, ChevronRight -> MUI equivalents
- lucide-react BookOpen, Clock, GraduationCap, School -> MUI equivalents
- lucide-react Calendar, MapPin, Edit, Trash2, Plus -> MUI equivalents
- lucide-react ArrowLeft, FileText, CheckCircle, XCircle -> MUI equivalents

Fixes build error: Failed to resolve import 'lucide-react'

src/components/common/Modal.tsx

@@ -1,5 +1,5 @@
 import React from 'react';
-import { X } from 'lucide-react';
+import { CloseIcon } from '@mui/icons-material';
 
 interface ModalProps {
   isOpen: boolean;
@@ -32,7 +32,7 @@ const Modal: React.FC<ModalProps> = ({ isOpen, onClose, title, children, maxWidt
               onClick={onClose}
               className="text-gray-400 hover:text-gray-500 focus:outline-none"
             >
-              <X size={20} />
+              <CloseIcon size={20} />
             </button>
           </div>