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_retries.go

@@ -2,7 +2,6 @@ package handlers
 
 import (
 	"errors"
-	"net/http"
 	"strconv"
 	"strings"
 )
@@ -89,32 +88,3 @@ func retriesErrorMessage(err error) string {
 	return errRetriesInvalid.Error() +
 		", or 0 for fire-and-forget"
 }
-
-// targetMaxRetries reads and validates max_retries from a target edit
-// submission, answering the request with a 400 and reporting false
-// when the value is set but invalid.
-//
-// It and the create path (newTarget) both use parseMaxRetries and
-// retriesErrorMessage, so the two cannot come to disagree about what a
-// valid retry count is. The wording matches the timeout control on
-// the same submission.
-func targetMaxRetries(
-	w http.ResponseWriter,
-	r *http.Request,
-	fallback int,
-) (int, bool) {
-	retries, err := parseMaxRetries(
-		r.PostFormValue("max_retries"), fallback,
-	)
-	if err != nil {
-		http.Error(
-			w,
-			"Invalid max retries: "+retriesErrorMessage(err),
-			http.StatusBadRequest,
-		)
-
-		return 0, false
-	}
-
-	return retries, true
-}