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/web/src/components/tools/bulk-rename-settings.tsx

@@ -7,7 +7,7 @@ import { useFileStore } from "@/stores/file-store";
 export function BulkRenameSettings() {
   const { t } = useTranslation();
   const { files, processing, error, setProcessing, setError } = useFileStore();
-  const [pattern, setPattern] = useState("image-{{index}}");
+  const [pattern, setPattern] = useState("file-{{index}}");
   const [startIndex, setStartIndex] = useState(1);
   const [downloadReady, setDownloadReady] = useState(false);
 

apps/web/src/components/tools/find-duplicates-settings.tsx

@@ -155,7 +155,7 @@ export function FindDuplicatesSettings() {
     const url = URL.createObjectURL(blob);
     const a = document.createElement("a");
     a.href = url;
-    a.download = "unique-images.zip";
+    a.download = "unique-files.zip";
     a.click();
     URL.revokeObjectURL(url);
   }, [files, results, bestOverrides]);