fix: disable pdfjs worker for reliable WASM image decoding

The web worker runs in a blob: URL context where /pdfjs/ WASM
paths don't resolve, causing JPEG 2000 images to decode at
degraded quality. Disable worker so all decoding runs on the
main thread where static assets are reachable.

Also bumped render scale from 2x to 3x for near-print quality.

src/lib/components/BookletViewer.svelte

@@ -5,11 +5,9 @@
   import { X, ChevronLeft, ChevronRight, ZoomIn, ZoomOut, Maximize, RotateCw } from 'lucide-svelte';
   import * as pdfjsLib from 'pdfjs-dist';
 
-  // Configure worker
-  pdfjsLib.GlobalWorkerOptions.workerSrc = new URL(
-    'pdfjs-dist/build/pdf.worker.min.mjs',
-    import.meta.url
-  ).toString();
+  // No web worker — run pdfjs on main thread so WASM files
+  // at /pdfjs/ are resolvable (workers use blob: URLs where
+  // relative paths break). Fine for a simple booklet viewer.
 
   interface Props {
     isOpen: boolean;
@@ -51,13 +49,15 @@
       const bytes = await invoke<number[]>('v2_fetch_url_bytes', { url });
       const data = new Uint8Array(bytes);
 
+      // disableWorker: run all decoding on main thread so WASM resolves
       const loadingTask = pdfjsLib.getDocument({
         data,
         disableRange: true,
         disableAutoFetch: true,
+        disableWorker: true,
         useWorkerFetch: false,
-        wasmUrl: '/pdfjs/',
-      });
+        wasmUrl: `${window.location.origin}/pdfjs/`,
+      } as any);
 
       pdfDoc = await loadingTask.promise;
       totalPages = pdfDoc.numPages;
@@ -84,8 +84,8 @@
     try {
       const page = await pdfDoc.getPage(currentPage);
       const dpr = window.devicePixelRatio || 1;
-      // Render at 2x DPR for sharp output (PDF points → pixels)
-      const qualityScale = 2;
+      // Render at 3x for near-print quality (216 DPI at 1x screens)
+      const qualityScale = 3;
       const scale = zoom * dpr * qualityScale;
       const viewport = page.getViewport({ scale, rotation });