test(integration): clean up background-removal test-harness leftovers (#281)

backgroundRemoval.integration.test.ts exported seedSubmission for no reason — nothing imports it, since draftingBackgroundRemoval.integration.test.ts and adminItemDrafts.integration.test.ts each wrote their own seeding helpers. Dropped the export, kept the function for local use.

All three of these suites create a temporary uploads directory with mkdtemp and point UPLOADS_DIR at it, but none of them removed the directory afterward or restored the previous UPLOADS_DIR value — checked and the leak existed in all three, not just the one the review flagged. Each afterEach now removes its temp directory with fs.rm and restores (or deletes) UPLOADS_DIR to what it held before the test touched it, so this suite no longer leaves rubbish in the OS temp directory or a stale environment variable for whatever runs after it in the same process.

This is test scaffolding cleanup, not a feature change — no runtime path in the application deletes anything.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

backend/tests/integration/draftingBackgroundRemoval.integration.test.ts

@@ -27,6 +27,7 @@ const PNG_BYTES = Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a, 0
 
 let uploads = '';
 let stub: http.Server | null = null;
+let previousUploadsDir: string | undefined;
 
 beforeEach(async () => {
   await resetDb();
@@ -51,6 +52,7 @@ beforeEach(async () => {
   resetAnthropicClient();
 
   uploads = await fsp.mkdtemp(path.join(os.tmpdir(), 'workerbg-'));
+  previousUploadsDir = process.env.UPLOADS_DIR;
   process.env.UPLOADS_DIR = uploads;
 
   stub = http.createServer((req, res) => {
@@ -72,6 +74,13 @@ afterEach(async () => {
     await new Promise<void>((resolve) => stub!.close(() => resolve()));
     stub = null;
   }
+  if (uploads !== '') {
+    await fsp.rm(uploads, { recursive: true, force: true });
+    uploads = '';
+  }
+  if (previousUploadsDir === undefined) delete process.env.UPLOADS_DIR;
+  else process.env.UPLOADS_DIR = previousUploadsDir;
+  previousUploadsDir = undefined;
 });
 
 afterAll(async () => {