feat(web): apply Otter Orange design system and UI improvements

Adopt the landing page's Otter Orange (#E07832) design system across
the web app, replacing the generic blue (#2563eb) theme. Light mode
uses warm cream/stone neutrals, dark mode uses deep brown tones.

UI changes:
- Remove Quick Actions section from home page
- Add modality filter tabs to file-uploaded view
- Remove colored left-border accents from tool panels and grid cards
- Use standard dropzone for pdf-to-image (custom-results mode)
- Fix PDF document viewer to use ArrayBuffer instead of blob URL
- Fix missing FileImage import in dropzone

apps/web/src/components/tools/document-view.tsx

@@ -29,14 +29,17 @@ export function DocumentView() {
 
   /* C+D: cancel in-flight renders and destroy the doc proxy on cleanup. */
   useEffect(() => {
-    if (!src || !canvasRef.current) return;
+    if (!canvasRef.current) return;
+    const file = entry?.file;
+    if (!file && !src) return;
     let cancelled = false;
     let doc: pdfjs.PDFDocumentProxy | undefined;
     let renderTask: pdfjs.RenderTask | undefined;
 
     (async () => {
       try {
-        doc = await pdfjs.getDocument({ url: src }).promise;
+        const source = file ? { data: new Uint8Array(await file.arrayBuffer()) } : { url: src! };
+        doc = await pdfjs.getDocument(source).promise;
         if (cancelled) return;
         setPageCount(doc.numPages);
         const pdfPage = await doc.getPage(Math.min(page, doc.numPages));
@@ -60,7 +63,7 @@ export function DocumentView() {
       renderTask?.cancel();
       doc?.loadingTask.destroy();
     };
-  }, [src, page]);
+  }, [src, page, entry?.file]);
 
   if (!entry) return null;