enhance: Improve validation errors for secrets/variables (#39221)

Signed-off-by: Ross Golder <ross@golder.org>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

templates/shared/variables/variable_list.tmpl

@@ -76,9 +76,9 @@
 				<input autofocus required
 					name="name"
 					id="dialog-variable-name"
-					value="{{.name}}"
 					pattern="^(?!GITEA_|GITHUB_)[a-zA-Z_][a-zA-Z0-9_]*$"
-					placeholder="{{ctx.Locale.Tr "secrets.creation.name_placeholder"}}"
+					data-tooltip-content="{{ctx.Locale.Tr "secrets.creation.name_pattern"}}"
+					placeholder="MY_VARIABLE_NAME"
 				>
 			</div>
 			<div class="field">