Fixes, new sort option "Last Completed"

frontend/src/app/library/LibraryContent.tsx

@@ -16,7 +16,7 @@ import { useLibraryLayout } from '../../hooks/useLibraryLayout';
 import { useLibraryFilters, clearLibraryFilters } from '../../hooks/useLibraryFilters';
 
 type ViewMode = 'grid' | 'list';
-type SortOption = 'createdAt' | 'title' | 'authorName' | 'rating' | 'wordCount' | 'lastReadAt';
+type SortOption = 'createdAt' | 'title' | 'authorName' | 'rating' | 'wordCount' | 'lastReadAt' | 'lastCompletedAt';
 
 export default function LibraryContent() {
   const router = useRouter();

frontend/src/components/library/MinimalLayout.tsx

@@ -67,6 +67,7 @@ export default function MinimalLayout({
   const getSortDisplayText = () => {
     const sortLabels: Record<string, string> = {
       lastReadAt: 'Last Read',
+      lastCompletedAt: 'Last Completed',
       createdAt: 'Date Added',
       title: 'Title',
       authorName: 'Author',

frontend/src/components/library/SidebarLayout.tsx

@@ -124,6 +124,7 @@ export default function SidebarLayout({
           >
             <option value="lastReadAt_desc">Last Read ↓</option>
             <option value="lastReadAt_asc">Last Read ↑</option>
+            <option value="lastCompletedAt_desc">Last Completed ↓</option>
             <option value="createdAt_desc">Date Added ↓</option>
             <option value="createdAt_asc">Date Added ↑</option>
             <option value="title_asc">Title ↑</option>
@@ -227,6 +228,7 @@ export default function SidebarLayout({
               className="flex-1 px-3 py-2 border rounded-lg theme-card border-gray-300 dark:border-gray-600"
             >
               <option value="lastReadAt">Last Read</option>
+              <option value="lastCompletedAt">Last Completed</option>
               <option value="createdAt">Date Added</option>
               <option value="title">Title</option>
               <option value="authorName">Author</option>

frontend/src/components/library/ToolbarLayout.tsx

@@ -112,6 +112,7 @@ export default function ToolbarLayout({
             >
               <option value="lastReadAt_desc">Sort: Last Read ↓</option>
               <option value="lastReadAt_asc">Sort: Last Read ↑</option>
+              <option value="lastCompletedAt_desc">Sort: Last Completed ↓</option>
               <option value="createdAt_desc">Sort: Date Added ↓</option>
               <option value="createdAt_asc">Sort: Date Added ↑</option>
               <option value="title_asc">Sort: Title ↑</option>

frontend/src/types/api.ts

@@ -18,6 +18,7 @@ export interface Story {
   readingPosition?: number;
   readingProgressPercentage?: number; // Pre-calculated percentage (0-100) from backend
   lastReadAt?: string;
+  lastCompletedAt?: string;
   createdAt: string;
   updatedAt: string;
 }