feat: add user authentication with separate login and register pages

- Custom User model with email as unique identifier (AUTH_USER_MODEL)

- POST /api/auth/register/ with email validation, password min 8 chars, duplicate rejection

- POST /api/auth/login/ returning JWT (access + refresh) tokens

- Passwords hashed via Django's make_password

- React LoginPage and RegisterPage with form validation

- AuthContext with useReducer for auth state management

- Axios API client with JWT token injection

- TypeScript conversion of frontend scaffold

api/accounts/models.py

@@ -0,0 +1,29 @@
+from django.contrib.auth.models import AbstractUser
+from django.db import models
+
+
+class User(AbstractUser):
+    """Custom User model using email as the unique identifier."""
+
+    email = models.EmailField(
+        unique=True,
+        max_length=254,
+        help_text="Email address used for authentication.",
+    )
+    username = models.CharField(
+        max_length=150,
+        blank=True,
+        null=True,
+        help_text="Optional display name. Not used for authentication.",
+    )
+
+    USERNAME_FIELD = "email"
+    REQUIRED_FIELDS: list[str] = []
+
+    class Meta:
+        db_table = "accounts_user"
+        verbose_name = "User"
+        verbose_name_plural = "Users"
+
+    def __str__(self) -> str:
+        return self.email