fix: handle non-image modalities across uploads, previews, and filenames (#255)

SnapOtter spans five modalities now, but several code paths still assumed image input.

- dropzone: default to accept-all when no fileFilter is given (image tools still pass one); neutral "supported file types" error text instead of "image files"
- automate (pipelines): accept any modality in the file pickers and dropzones; render modality-aware previews (video player, audio waveform, document/data card) instead of always using ImageViewer/BeforeAfterSlider
- filename sanitizer: extend the double-extension allowlist beyond image extensions to video/audio/document/data so e.g. "report.csv.php" becomes "report.csv"; add tests
- thumbnail route: return 422 for non-rasterisable files (audio, data, non-PDF docs) instead of attempting a doomed Sharp decode
- pool: unknown tools fall back to the "system" pool, not the image pool
- a11y labels: "Previous/Next image", "Image viewer/area/controls/drop zone" are now modality-neutral, across all 21 locales
- copy: bulk-rename default, find-duplicates ZIP name, SSRF user-agent, fetch-urls fallback name, file-details MIME label, URL-import placeholder, help dialog

apps/api/src/routes/fetch-urls.ts

@@ -110,7 +110,7 @@ function filenameFromUrl(url: string): string {
   } catch {
     // ignore parse errors
   }
-  return `image-${randomUUID().slice(0, 8)}`;
+  return `file-${randomUUID().slice(0, 8)}`;
 }
 
 /**

apps/api/src/routes/user-files.ts

@@ -524,6 +524,12 @@ export async function userFileRoutes(app: FastifyInstance): Promise<void> {
 
         // Image thumbnail (existing path)
         const validation = await validateImageBuffer(rawBuffer, file.originalName);
+        if (!validation.valid) {
+          // Audio, data, and non-PDF document files have no raster thumbnail.
+          // Return 422 (not 204) so the client's <img> onError falls back to a
+          // modality icon instead of attempting a doomed Sharp decode below.
+          return reply.status(422).send({ error: "No thumbnail available for this file type" });
+        }
         let decoded: Buffer<ArrayBuffer> = Buffer.from(rawBuffer);
         if (validation.valid && validation.format === "heif") {
           decoded = Buffer.from(await decodeHeic(rawBuffer));