audit 4: findings of the two reviews

- Two inbound domains on one upstream could never change its TLS mode,
  each save refused for the other (medium): SetTransportAs changes the
  mode for every domain on the upstream when the one saving may change
  them all; a domain user who may not is refused with the mode, not the
  other tenant's domain name (security F1: the first version named it).
- A deletion's leftover DKIM key is removed by Resync (Reload
  configuration, a restore's first start) for names no domain has.
- The backup's write deadline moves before Check.
- hasUnsavedEdit skips password and file fields and compares a multiple
  select's options; htmx.config.timeout 30 s, so a refresh never answered
  ends and is tried again; a failed refresh's promise is handled.
- An empty filtered Outbound log says no message matches the filters.
- The dummy bcrypt hash is made at start; a DMARC part over 8 MiB is
  refused for its size like the other two limits.
- Health's Configuration box says what Reload writes (design first,
  32dfe4a).
- Docs: CHANGELOG, guide § Inbound, security.md (the shared upstream's
  mode, the profile form's "username taken"), architecture.md (owed to an
  address), the plan's notes corrected.
Tests: the shared upstream (service, handler), the leftover key, all eight
Health boxes ordered, the subject from before migration 0011, the new JS
cases.

Tested on the test server: go vet + go test of 25 packages, make e2e (all
pass, 636 s) on this tree.

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

internal/domain/delete_test.go

@@ -50,6 +50,23 @@ func TestDeleteRunsEveryRebuildAndSaysTheDomainIsGone(t *testing.T) {
 	if _, err := os.Stat(keyDir); err != nil {
 		t.Errorf("the key went while the tables may still name it: %v", err)
 	}
+
+	// Reload configuration finishes the deletion: the tables rebuilt, the
+	// key of a domain that is gone goes too; the others' stay.
+	odk.reload = func() error { return nil }
+	keep, err := s.Add("kept.example")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := s.Resync(); err != nil {
+		t.Fatalf("Resync: %v", err)
+	}
+	if _, err := os.Stat(keyDir); !os.IsNotExist(err) {
+		t.Errorf("the deleted domain's key is still there after Resync: %v", err)
+	}
+	if _, err := os.Stat(filepath.Join(odk.keysDir, keep.Name)); err != nil {
+		t.Errorf("Resync removed a domain's key: %v", err)
+	}
 }
 
 // The sender map failing is the same: deleted, said so; the tables were