Fix some pending problems (#29985)

These changes are quite independent and trivial, so I don't want to open
too many PRs.

* https://github.com/go-gitea/gitea/pull/29882#discussion_r1529607091
    * the `f.Close` should be called properly
* the error message could be more meaningful
(https://github.com/go-gitea/gitea/pull/29882#pullrequestreview-1942557935)
*
https://github.com/go-gitea/gitea/pull/29859#pullrequestreview-1942324716
    * the new translation strings don't take arguments
* https://github.com/go-gitea/gitea/pull/28710#discussion_r1443778807
    * stale for long time
*  #28140 
    * a form was forgotten to be changed to work with backend code

modules/markup/csv/csv.go

@@ -124,9 +124,8 @@ func (Renderer) fallbackRender(input io.Reader, tmpBlock *bufio.Writer) error {
 			return err
 		}
 	}
-	err = scan.Err()
-	if err != nil {
-		return fmt.Errorf("scan: %w", err)
+	if err = scan.Err(); err != nil {
+		return fmt.Errorf("fallbackRender scan: %w", err)
 	}
 
 	_, err = tmpBlock.WriteString("</pre>")