refactor: 清理前端 createAsset 死代码和未使用 import

- 删除 test/api/assets.test.ts 中 createAsset 的 import 和测试块
- 删除 GeneratePage.test.tsx 和 VoiceMaterialLibrary.test.tsx 中 createAsset mock
- 清理 voices/types.ts 和 voice-materials/types.ts 中 createAsset 注释
- 删除 useVoiceUpload.ts 中未使用的 IngestJob type import

apps/web/src/test/api/assets.test.ts

@@ -7,7 +7,6 @@ import {
   deleteAssetLibrary,
   getAssets,
   getAssetsByKind,
-  createAsset,
   updateAsset,
   updateAssetReviewStatus,
   deleteAsset,
@@ -175,22 +174,6 @@ describe("assets API", () => {
     })
   })
 
-  describe("createAsset", () => {
-    it("should resolve successfully", async () => {
-      await expect(createAsset({ name: "test-item" })).resolves.not.toThrow()
-    })
-
-    it("should reject on API error", async () => {
-      mockGet.mockRejectedValue(new Error("Network error"))
-      mockPost.mockRejectedValue(new Error("Network error"))
-      mockPut.mockRejectedValue(new Error("Network error"))
-      mockDelete.mockRejectedValue(new Error("Network error"))
-      mockPatch.mockRejectedValue(new Error("Network error"))
-
-      await expect(createAsset({ name: "test-item" })).rejects.toThrow()
-    })
-  })
-
   describe("updateAsset", () => {
     it("should resolve successfully", async () => {
       await expect(updateAsset("test-assetId")).resolves.not.toThrow()