Thumbnail upload PUT sends the signed Content-MD5 (closes #238)

`/files/upload-url` signs the content MD5 into the presigned URL, so
storage refused the PUT that `putFile` sent without it. `putFile` now
takes the MD5 given to `getUploadURL` and sends it. The thumbnail test's
fake storage refuses a PUT without the signed header.

Model: opus-5-5

test/api/upload.test.ts

@@ -80,13 +80,20 @@ describe("ApiClient.putFile", () => {
         const client = new ApiClient({ fetch, authToken: "secret-tok" });
         const data = new Uint8Array([1, 2, 3, 4, 5]);
 
-        await client.putFile("https://s3.example.com/presigned?sig=abc", data);
+        await client.putFile(
+            "https://s3.example.com/presigned?sig=abc",
+            data,
+            "md5base64==",
+        );
 
         expect(calls[0]!.url).toBe("https://s3.example.com/presigned?sig=abc");
         expect(calls[0]!.init?.method).toBe("PUT");
         const headers = new Headers(calls[0]!.init?.headers as HeadersInit);
         expect(headers.get("Content-Type")).toBe("application/octet-stream");
         expect(headers.get("Content-Length")).toBe("5");
+        // The server signs the MD5 into the URL; storage refuses the PUT
+        // without it.
+        expect(headers.get("Content-MD5")).toBe("md5base64==");
         // Must NOT leak auth headers to S3
         expect(headers.has("X-Auth-Token")).toBe(false);
         expect(headers.has("X-Client-Package")).toBe(false);
@@ -99,7 +106,11 @@ describe("ApiClient.putFile", () => {
         const client = new ApiClient({ fetch });
 
         await expect(
-            client.putFile("https://s3.example.com/bad", new Uint8Array(10)),
+            client.putFile(
+                "https://s3.example.com/bad",
+                new Uint8Array(10),
+                "md5base64==",
+            ),
         ).rejects.toThrow(/403/);
     });
 });