feat: use cloud backend thumbnail resize for image previews (#9298)

## Summary

- In cloud mode, large generated images (4K, 8K+) cause browser freezing
when loaded at full resolution for preview display
- The cloud backend (ingest service) now supports a `res` query
parameter on `/api/view` that returns server-side resized JPEG (quality
80, max 512px) instead of redirecting to the full-size GCS original
- This PR adds `&res=512` to all image preview URLs in cloud mode,
reducing browser decode overhead from tens of MB to tens of KB
- Downloads still use the original resolution (no `res` param)
- No impact on localhost/desktop builds (`isCloud` compile-time
constant)

### without `?res`

302 -> png downloads
<img width="808" height="564" alt="스크린샷 2026-02-28 오후 6 53 03"
src="https://github.com/user-attachments/assets/7c1c62dd-0bc4-468d-9c74-7b98e892e126"
/>
<img width="323" height="137" alt="스크린샷 2026-02-28 오후 6 52 52"
src="https://github.com/user-attachments/assets/926aa0c4-856c-4057-96a0-d8fbd846762b"
/>

200 -> jpeg

### with `?res`
<img width="811" height="407" alt="스크린샷 2026-02-28 오후 6 51 55"
src="https://github.com/user-attachments/assets/d58d46ae-6749-4888-8bad-75344c4d868b"
/>


### Changes

- **New utility**: `getCloudResParam(filename?)` returns `&res=512` in
cloud mode for image files, empty string otherwise
- **Core stores**: `imagePreviewStore` appends `res` to node output
URLs; `queueStore.ResultItemImpl` gets a `previewUrl` getter (separates
preview from download URLs)
- **Applied to**: asset browser thumbnails, widget dropdown previews,
linear mode indicators, image compare node, background image upload

### Intentionally excluded

- Downloads (`getAssetUrl`) — need original resolution
- Mask editor — needs pixel-accurate data
- Audio/video/3D files — `res` only applies to raster images
- Execution-in-progress previews — use WebSocket blob URLs, not
`/api/view`

## Test plan

- [x] Unit tests for `getCloudResParam()` (5 tests: cloud/non-cloud,
image/non-image, undefined filename)
- [x] `pnpm typecheck` passes
- [x] `pnpm lint` passes
- [x] All 5332 unit tests pass
- [x] Manual verification on cloud.comfy.org: `res=512` returns 200 with
resized JPEG; without `res` returns 302 redirect to GCS PNG original

---------

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

src/stores/imagePreviewStore.ts

@@ -10,6 +10,7 @@ import type {
   ResultItem,
   ResultItemType
 } from '@/schemas/apiSchema'
+import { appendCloudResParam } from '@/platform/distribution/cloudPreviewUtil'
 import { api } from '@/scripts/api'
 import { app } from '@/scripts/app'
 import type { NodeLocatorId } from '@/types/nodeIdentification'
@@ -118,10 +119,13 @@ 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 imgUrlPart = new URLSearchParams(image)
-      return api.apiURL(`/view?${imgUrlPart}${previewParam}${rand}`)
+      const params = new URLSearchParams(image)
+      if (isImage) appendCloudResParam(params, firstFilename)
+      return api.apiURL(`/view?${params}${previewParam}${rand}`)
     })
   }
 

src/stores/queueStore.ts

@@ -14,6 +14,7 @@ import type {
   StatusWsMessageStatus,
   TaskOutput
 } from '@/schemas/apiSchema'
+import { appendCloudResParam } from '@/platform/distribution/cloudPreviewUtil'
 import { api } from '@/scripts/api'
 import type { ComfyApp } from '@/scripts/app'
 import { useExtensionService } from '@/services/extensionService'
@@ -91,6 +92,13 @@ export class ResultItemImpl {
     return api.apiURL('/view?' + this.urlParams)
   }
 
+  get previewUrl(): string {
+    if (!this.isImage) return this.url
+    const params = new URLSearchParams(this.urlParams)
+    appendCloudResParam(params, this.filename)
+    return api.apiURL('/view?' + params)
+  }
+
   get urlWithTimestamp(): string {
     return `${this.url}&t=${+new Date()}`
   }