비디오의 경우 원하는 장면으로 썸네일을 변경할 수 있도록 개선

src/routes/(fullscreen)/file/[id]/service.ts

@@ -1,9 +1,37 @@
 import { callPostApi } from "$lib/hooks";
-import type { CategoryFileAddRequest } from "$lib/server/schemas";
+import { encryptData } from "$lib/modules/crypto";
+import { storeFileThumbnailCache } from "$lib/modules/file";
+import type { CategoryFileAddRequest, FileThumbnailUploadRequest } from "$lib/server/schemas";
 
 export { requestCategoryCreation, requestFileRemovalFromCategory } from "$lib/services/category";
 export { requestFileDownload } from "$lib/services/file";
 
+export const requestThumbnailUpload = async (
+  fileId: number,
+  thumbnail: Blob,
+  dataKey: CryptoKey,
+  dataKeyVersion: Date,
+) => {
+  const thumbnailBuffer = await thumbnail.arrayBuffer();
+  const thumbnailEncrypted = await encryptData(thumbnailBuffer, dataKey);
+
+  const form = new FormData();
+  form.set(
+    "metadata",
+    JSON.stringify({
+      dekVersion: dataKeyVersion.toISOString(),
+      contentIv: thumbnailEncrypted.iv,
+    } satisfies FileThumbnailUploadRequest),
+  );
+  form.set("content", new Blob([thumbnailEncrypted.ciphertext]));
+
+  const res = await fetch(`/api/file/${fileId}/thumbnail/upload`, { method: "POST", body: form });
+  if (!res.ok) return false;
+
+  storeFileThumbnailCache(fileId, thumbnailBuffer); // Intended
+  return true;
+};
+
 export const requestFileAdditionToCategory = async (fileId: number, categoryId: number) => {
   const res = await callPostApi<CategoryFileAddRequest>(`/api/category/${categoryId}/file/add`, {
     file: fileId,