Fix ESLint errors

Author: jq1836

frontend/components/questions/question-filter.tsx

@@ -66,7 +66,9 @@ const QuestionFilter: React.FC<QuestionFilterProps> = ({
               <SelectContent>
                 <SelectItem value="all">All</SelectItem>
                 {CategoryEnumArray.map((category) => (
-                  <SelectItem value={category}>{category}</SelectItem>
+                  <SelectItem key={category} value={category}>
+                    {category}
+                  </SelectItem>
                 ))}
               </SelectContent>
             </Select>
@@ -83,7 +85,9 @@ const QuestionFilter: React.FC<QuestionFilterProps> = ({
               <SelectContent>
                 <SelectItem value="all">All</SelectItem>
                 {ComplexityEnumArray.map((complexity) => (
-                  <SelectItem value={complexity}>{complexity}</SelectItem>
+                  <SelectItem key={complexity} value={complexity}>
+                    {complexity}
+                  </SelectItem>
                 ))}
               </SelectContent>
             </Select>

frontend/components/questions/question-form-modal.tsx

@@ -124,7 +124,7 @@ const QuestionFormModal: React.FC<QuestionFormModalProps> = ({ ...props }) => {
                       </SelectTrigger>
                       <SelectContent>
                         {ComplexityEnumArray.map((complexity) => (
-                          <SelectItem value={complexity}>
+                          <SelectItem key={complexity} value={complexity}>
                             {complexity}
                           </SelectItem>
                         ))}

frontend/components/ui/multi-select.tsx

@@ -1,5 +1,7 @@
 // src/components/multi-select.tsx
 
+/* eslint-disable no-unused-vars */
+
 import * as React from "react";
 import { cva, type VariantProps } from "class-variance-authority";
 import {