Keep what was typed when a target or webhook edit is refused (closes #381)

A refused save on the target edit page answered with a bare text page, losing the form and everything typed, and the webhook edit page came back with the stored values instead of the submitted ones. A refused target edit now shows the edit form again with the reason above it and every value submitted, with the same status codes as before; a refused webhook edit keeps the submitted name, description and retention. Target edits use the same validation as new targets, with no second copy; an encoding or database failure stays a logged 500. The browser test covers a refused save on both pages, and its main function is now a plain list of checks.

Model: opus-5-5

internal/handlers/target_private_refusal_test.go

@@ -44,9 +44,9 @@ func TestTargetRefusal_PrivateDestinationSaysHowToAllowIt(
 			form.Set("type", string(targetType))
 			form.Set("url", editBlockedURL)
 
-			// A refused add shows the webhook page again, where
-			// the hint is HTML-escaped; a refused edit answers in
-			// plain text.
+			// A refused add shows the webhook page again, and a
+			// refused edit the edit page, where the hint is
+			// HTML-escaped.
 			added := serveTarget(
 				env, http.MethodPost, targetsPath, form,
 			)
@@ -76,7 +76,8 @@ func TestTargetRefusal_PrivateDestinationSaysHowToAllowIt(
 			)
 			assert.Equal(t, http.StatusBadRequest, edited.Code)
 			assert.Contains(
-				t, edited.Body.String(), privateRefusalHint,
+				t, edited.Body.String(),
+				html.EscapeString(privateRefusalHint),
 			)
 		})
 	}