feat: add back button to test edit form

TestForm now accepts optional onBack/backLabel props.
TestEdit passes 'К просмотру теста' back button when in edit mode.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/TestForm/index.tsx

@@ -1,4 +1,4 @@
-import { MinusCircleOutlined, PlusOutlined } from '@ant-design/icons'
+import { ArrowLeftOutlined, MinusCircleOutlined, PlusOutlined } from '@ant-design/icons'
 import {
   Button,
   Card,
@@ -11,6 +11,7 @@ import {
   Typography,
 } from 'antd'
 
+
 const { Title } = Typography
 
 const EMPTY_ANSWER = { text: '', is_correct: false }
@@ -33,6 +34,8 @@ interface TestFormProps {
   isPending: boolean
   submitLabel: string
   onCancel: () => void
+  onBack?: () => void
+  backLabel?: string
 }
 
 export default function TestForm({
@@ -42,6 +45,8 @@ export default function TestForm({
   isPending,
   submitLabel,
   onCancel,
+  onBack,
+  backLabel = 'Назад',
 }: TestFormProps) {
   const [form] = Form.useForm<TestFormValues>()
 
@@ -55,6 +60,15 @@ export default function TestForm({
 
   return (
     <div style={{ maxWidth: 820, margin: '0 auto', padding: 24 }}>
+      {onBack && (
+        <Button
+          icon={<ArrowLeftOutlined />}
+          onClick={onBack}
+          style={{ marginBottom: 16 }}
+        >
+          {backLabel}
+        </Button>
+      )}
       <Title level={2}>{heading}</Title>
 
       <Form form={form} layout="vertical" onFinish={onSubmit} initialValues={defaultValues}>

frontend/src/pages/TestEdit/index.tsx

@@ -92,6 +92,8 @@ export default function TestEdit() {
         isPending={isPending}
         submitLabel="Сохранить"
         onCancel={() => setEditMode(false)}
+        onBack={() => setEditMode(false)}
+        backLabel="К просмотру теста"
       />
     )
   }