add email setting, closes #5. other misc small fixes

accounts/models.py

@@ -17,6 +17,11 @@ class CustomUser(AbstractUser):
         verbose_name="Show Friend Code on Link Previews",
         help_text="This will primarily affect share link previews on X, Discord, etc."
     )
+    enable_email_notifications = models.BooleanField(
+        default=True,
+        verbose_name="Enable Email Notifications",
+        help_text="Receive new trade notifications via email."
+    )
     reputation_score = models.IntegerField(default=0)
 
     def __str__(self):