refactor: unify image classification and fix cloud preview param handling (#9408)

## Summary

Addresses review feedback from PR #9298 and resolves the divergence
between `ResultItemImpl.isImage` and `appendCloudResParam`'s image
classification.

### Changes

- **Unify suffix-based classification**: Replace narrow
`isImageBySuffix` (gif/webp only), `isVideoBySuffix` (webm/mp4), and
`isAudioBySuffix` with `getMediaTypeFromFilename()` from
shared-frontend-utils, using the same `IMAGE_EXTENSIONS` set (png, jpg,
jpeg, gif, webp, bmp, avif, tif, tiff) that `appendCloudResParam` uses
- **imageCompare.ts**: Pass `record.filename` to `appendCloudResParam`
(was called without filename, bypassing image-extension guard)
- **imagePreviewStore.ts**: Use per-image `image.filename` instead of
first image's filename for all images in batch
- **LinearControls.vue**: Use `resultItem.filename` (already a string)
instead of `String(filename)` which converts undefined to `"undefined"`

### Related review comments

- [imageCompare.ts — missing
filename](https://github.com/Comfy-Org/ComfyUI_frontend/pull/9298#discussion_r2886137498)
- [imagePreviewStore.ts — per-image
filename](https://github.com/Comfy-Org/ComfyUI_frontend/pull/9298#discussion_r2886138718)
- [LinearControls.vue —
String(filename)](https://github.com/Comfy-Org/ComfyUI_frontend/pull/9298#discussion_r2886140159)
- [queueStore.ts — diverging image
classification](https://github.com/Comfy-Org/ComfyUI_frontend/pull/9298#discussion_r2886142886)

## Test plan

- [x] 66 unit tests pass (queueStore + cloudPreviewUtil)
- [x] `pnpm typecheck` passes
- [x] `pnpm lint` passes

- Fixes #9386

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src/stores/nodeOutputStore.ts

@@ -121,11 +121,10 @@ export const useNodeOutputStore = defineStore('nodeOutput', () => {
     const rand = app.getRandParam()
     const previewParam = getPreviewParam(node, outputs)
     const isImage = isImageOutputs(node, outputs)
-    const firstFilename = outputs.images[0]?.filename
 
     return outputs.images.map((image) => {
       const params = new URLSearchParams(image)
-      if (isImage) appendCloudResParam(params, firstFilename)
+      if (isImage) appendCloudResParam(params, image.filename)
       return api.apiURL(`/view?${params}${previewParam}${rand}`)
     })
   }