fix: 登录页entity_id存储取login响应顶层字段 — user对象无entity_id导致cma_entity_id恒为1

- login响应结构: {token, entity_id, entity_name, entity_short_name, user:{...}}
- 原代码读 res.user?.entity_id ?? 1 → 登录博海(2)却存1 → 页面显式传参1与token绑定2不一致 → get_entity_id返回403
- 改为 res.entity_id / res.entity_short_name（与MainLayout切换器存储逻辑一致）

frontend/src/views/Login.vue

@@ -60,8 +60,8 @@ async function handleLogin() {
     const res: any = await authApi.login({ ...form, entity_id: Number(form.entity_id) })
     localStorage.setItem('cma_token', res.token)
     localStorage.setItem('cma_user', JSON.stringify(res.user))
-    localStorage.setItem('cma_entity_id', String(res.user?.entity_id ?? 1))
-    localStorage.setItem('cma_entity_name', res.user?.entity_short_name || res.user?.entity_name || '')
+    localStorage.setItem('cma_entity_id', String(res.entity_id ?? res.user?.entity_id ?? 1))
+    localStorage.setItem('cma_entity_name', res.entity_short_name || res.entity_name || '')
     router.push('/dashboard')
   } catch (e: any) {
     ElMessage.error(e?.response?.data?.detail || '登录失败')