upload_spool: spool 403 (node not approved yet) instead of deleting (node-26#44)

A node waiting on approval would otherwise lose every call it records. The
512 MiB / 72h spool caps bound what a never-approved node keeps. 400 and 413
are still deleted.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

drb-edge-node/tests/test_upload_spool.py

@@ -61,7 +61,7 @@ def _spool(tmp_path: Path, uploader, clock=None, **kw) -> UploadSpool:
     (500, None, RETRY),
     (503, None, RETRY),
     (400, None, REJECT),
-    (403, None, REJECT),
+    (403, None, RETRY),      # not approved yet: approval may still come
     (413, None, REJECT),
 ])
 def test_classify(status, url, kind):
@@ -111,7 +111,7 @@ async def test_successful_upload_deletes_the_file(tmp_path, recorder, monkeypatc
 
 
 async def test_rejected_upload_is_not_spooled(tmp_path, recorder, monkeypatch):
-    _patch_post(monkeypatch, UploadResult(REJECT, status=403, detail="HTTP 403: Node is not approved"))
+    _patch_post(monkeypatch, UploadResult(REJECT, status=413, detail="HTTP 413: File too large"))
     path = _recording(tmp_path)
     assert await recorder.upload_recording(path, "call-1") is None
     assert not path.exists()