fix(web): restore preview panel rendering for all file types

The home-page preview panel always rendered ImageViewer regardless of the
uploaded file's modality, causing videos, audio, PDFs, and data files to
show "Preview not available". Root cause: the preview branching only
checked for a blob URL and assumed all files were images.

Fix: branch on currentEntry.previewKind so the existing MediaPlayerView,
DocumentView, and a file-info fallback are activated for their respective
modalities. Also widen the AppLayout dropzone from image-only to all file
types so non-image files can reach the home page in the first place.

apps/web/src/components/layout/app-layout.tsx

@@ -148,7 +148,9 @@ export function AppLayout({
         className={cn("flex-1 flex flex-col overflow-hidden", isMobile && "pt-12 pb-20")}
       >
         <div className="flex-1 overflow-y-auto p-6 flex items-center justify-center">
-          {children || <Dropzone onFiles={onFiles} onUrlImport={onUrlImport} accept="image/*" />}
+          {children || (
+            <Dropzone onFiles={onFiles} onUrlImport={onUrlImport} fileFilter={() => true} />
+          )}
         </div>
       </main>