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/web/handlers/handlers_backup.go

@@ -79,6 +79,17 @@ func (h *Handlers) HandleBackup(w http.ResponseWriter, r *http.Request) {
 			logf("panel: full backup: %s", msg)
 		},
 	}
+	// The server's write deadline is for pages (cmd/panel newHTTPServer); an
+	// archive streams for as long as it takes, and the read-through before it
+	// (Check) is as long as the archive: the deadline moves first, so a
+	// refusal after a long Check can still be written (review of stage 4).
+	// Two hours carry a gigabyte at a little over 1 Mbit/s, and still end a
+	// client that keeps the connection and stops reading, which TCP alone
+	// would not (net/http, Go 1.26: ResponseController.SetWriteDeadline).
+	if err := http.NewResponseController(w).SetWriteDeadline(time.Now().Add(2 * time.Hour)); err != nil {
+		logf("panel: full backup: lift the write deadline: %v", err)
+	}
+
 	if err := backup.ValidateDeployRoot(h.cfg.DeployRoot); err != nil {
 		logf("panel: full backup: %v", err)
 		h.renderBackupPageWith(w, r, http.StatusBadRequest, "", deployBackupErr(err))
@@ -107,15 +118,6 @@ func (h *Handlers) HandleBackup(w http.ResponseWriter, r *http.Request) {
 	w.Header().Set("Content-Disposition", fmt.Sprintf("attachment; filename=%q", filename))
 	w.Header().Set("Cache-Control", "no-store")
 
-	// The server's write deadline is for pages (cmd/panel newHTTPServer); an
-	// archive streams for as long as it takes. Two hours carry a gigabyte at
-	// a little over 1 Mbit/s, and still end a client that keeps the
-	// connection and stops reading, which TCP alone would not (net/http, Go
-	// 1.26: ResponseController.SetWriteDeadline).
-	if err := http.NewResponseController(w).SetWriteDeadline(time.Now().Add(2 * time.Hour)); err != nil {
-		logf("panel: full backup: lift the write deadline: %v", err)
-	}
-
 	// Everything below streams: past this point headers (and possibly some
 	// bytes) are already on the wire, so a failure cannot switch to a clean
 	// error page. Log it and let the truncated download fail loudly on the