chore: 将后端移动到 api/ 目录，准备合并为单仓库

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

api/account/models.py

@@ -0,0 +1,50 @@
+from django.db import models
+from django.contrib.auth.models import AbstractUser
+
+
+class RoleChoices(models.TextChoices):
+    SUPER = "super", "超级管理员"
+    ADMIN = "admin", "管理员"
+    NORMAL = "normal", "普通"
+
+
+class User(AbstractUser):
+    first_name = None
+    last_name = None
+
+    role = models.CharField(
+        max_length=20,
+        choices=RoleChoices.choices,
+        default=RoleChoices.NORMAL,
+        verbose_name="权限",
+    )
+    raw_password = models.CharField(
+        max_length=20,
+        null=True,
+        blank=True,
+        verbose_name="明文密码",
+    )
+    classname = models.CharField(
+        max_length=50,
+        blank=True,
+        default="",
+        verbose_name="班级",
+    )
+
+    def save(self, *args, **kwargs):
+        if self.username:
+            if self.is_superuser:
+                self.role = RoleChoices.SUPER
+            super().save(*args, **kwargs)
+
+    def set_password(self, raw_password):
+        super().set_password(raw_password)
+        self.raw_password = raw_password
+        self.save()
+
+    class Meta:
+        ordering = ("-id",)
+        verbose_name = "用户"
+        verbose_name_plural = verbose_name
+
+