fix: N+1 query in BookSettings::recacheCovers()

Replace individual $book->update() calls with a single bulk UPDATE query.
File deletions and job dispatches still loop as needed.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: dotMavriQ

app/Livewire/Books/BookSettings.php

@@ -84,23 +84,27 @@ public function recacheCovers(): void
             })
             ->get();
 
-        $count = 0;
-
         foreach ($books as $book) {
-            // Delete existing local cover file if it exists
             if ($book->cover_url && str_starts_with($book->cover_url, '/storage/covers/')) {
                 $filename = str_replace('/storage/', '', $book->cover_url);
                 Storage::disk('public')->delete($filename);
             }
+        }
 
-            // Clear cover_url
-            $book->update(['cover_url' => null]);
+        Book::query()
+            ->where('user_id', Auth::id())
+            ->where(function ($query) {
+                $query->whereNotNull('isbn')
+                    ->orWhereNotNull('isbn13');
+            })
+            ->update(['cover_url' => null]);
 
-            // Dispatch job to fetch fresh cover
+        foreach ($books as $book) {
             FetchBookCover::dispatch($book->id);
-            $count++;
         }
 
+        $count = $books->count();
+
         session()->flash('message', "Re-caching covers for {$count} book(s). This runs in the background.");
     }