wire Mailtrap TestInbox config in DeepDrftAPI

Read AuthBlocks:Email:TestInbox from config (no throw — optional sandbox key). Add TestInbox placeholder to authblocks.example.json.

DeepDrftAPI/Program.cs

@@ -109,6 +109,7 @@ builder.Services.AddAuthBlocks(options =>
         ?? throw new InvalidOperationException("AuthBlocks:Email:Token is required");
     options.EmailConnection.FromAddress = builder.Configuration["AuthBlocks:Email:From"]
         ?? throw new InvalidOperationException("AuthBlocks:Email:From is required");
+    options.EmailConnection.TestInbox   = builder.Configuration["AuthBlocks:Email:TestInbox"];
 
     options.AdminUserSettings = new AdminUserSettings
     {

DeepDrftAPI/environment/authblocks.example.json

@@ -9,7 +9,8 @@
     "Email": {
       "Host": "smtp.your-provider.com",
       "Token": "your-email-token-here",
-      "From": "noreply@yourdomain.com"
+      "From": "noreply@yourdomain.com",
+      "TestInbox": ""
     },
     "Admin": {
       "UserName": "admin",