feat(home-banner): 轮播支持 PC/移动两端分图与热区跳转，热区图悬浮放大；修复上传压缩压白透明 PNG

frontend/src/shared/utils/imageUpload.spec.ts

@@ -0,0 +1,32 @@
+import { describe, expect, it } from 'vitest'
+import { resolveUploadEncoding } from './imageUpload'
+
+describe('resolveUploadEncoding', () => {
+  it('带透明通道的图必须输出 PNG，避免透明区域被压成实色', () => {
+    const encoding = resolveUploadEncoding('home-banner', true)
+
+    expect(encoding.outputType).toBe('image/png')
+    expect(encoding.extension).toBe('png')
+    expect(encoding.maxSide).toBe(1920)
+    expect(encoding.quality).toBe(0.84)
+  })
+
+  it('不透明图继续用 WebP 压缩', () => {
+    const encoding = resolveUploadEncoding('home-banner', false)
+
+    expect(encoding.outputType).toBe('image/webp')
+    expect(encoding.extension).toBe('webp')
+  })
+
+  it('未登记的 scene 使用兜底参数', () => {
+    const encoding = resolveUploadEncoding('unknown-scene', false)
+
+    expect(encoding.maxSide).toBe(1600)
+    expect(encoding.quality).toBe(0.82)
+  })
+
+  it('头像等小尺寸场景保留各自的边长上限', () => {
+    expect(resolveUploadEncoding('avatar', false).maxSide).toBe(512)
+    expect(resolveUploadEncoding('qrcode', true).maxSide).toBe(2560)
+  })
+})