chore: 从 git 中移除 backend/target 目录

- 使用 git rm --cached 从版本控制中删除 target 目录
- .gitignore 已配置忽略 target 和 node_modules
- 本地文件保留，仅从 git 索引中删除

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

frontend/src/views/Login.vue

@@ -36,6 +36,7 @@ import { ref, reactive } from 'vue'
 import { useRouter } from 'vue-router'
 import { ElMessage, type FormInstance, type FormRules } from 'element-plus'
 import { useUserStore } from '@/stores/user'
+import { hashPassword } from '@/utils/crypto'
 
 const router = useRouter()
 const userStore = useUserStore()
@@ -59,7 +60,12 @@ const handleLogin = async () => {
     if (valid) {
       loading.value = true
       try {
-        await userStore.login(loginForm)
+        // 对密码进行 SHA-256 哈希后再传输
+        const hashedPassword = await hashPassword(loginForm.password)
+        await userStore.login({
+          username: loginForm.username,
+          password: hashedPassword
+        })
         ElMessage.success('登录成功')
         router.push('/')
       } catch (error) {