feat: add governed postbox delivery and report hardening

src/govoplan_campaign/backend/response_security.py

@@ -110,6 +110,7 @@ def public_delivery_result_message(
     last_error: Any,
     send_status: Any,
     imap_status: Any,
+    postbox_status: Any = None,
 ) -> str | None:
     """Map persisted provider text to a stable business-safe explanation."""
 
@@ -117,10 +118,22 @@ def public_delivery_result_message(
         return None
     clean_send_status = str(send_status or "")
     clean_imap_status = str(imap_status or "")
+    clean_postbox_status = str(postbox_status or "")
+    if clean_postbox_status == "outcome_unknown":
+        return "Postbox delivery outcome requires operator reconciliation."
     if clean_send_status == "outcome_unknown":
-        return "SMTP delivery outcome requires operator reconciliation."
+        return "Delivery outcome requires operator reconciliation."
+    if clean_postbox_status in {
+        "rejected_temporary",
+        "rejected_permanent",
+    }:
+        return "Postbox delivery was rejected; an operator can inspect restricted diagnostics."
+    if clean_postbox_status == "partially_accepted":
+        return "Some Postbox targets accepted the message and others rejected it."
     if clean_send_status in {"failed_temporary", "failed_permanent"}:
-        return "SMTP delivery failed; an operator can inspect restricted diagnostics."
+        if clean_postbox_status in {"", "not_requested"}:
+            return "SMTP delivery failed; an operator can inspect restricted diagnostics."
+        return "Delivery failed; an operator can inspect restricted diagnostics."
     if clean_imap_status in {"outcome_unknown", "appending"}:
         return "Sent-folder append outcome requires operator reconciliation."
     if clean_imap_status in {"failed", "skipped"}: