feat(#251): Add waitlist notification builder and signup endpoint

JobFlow.API/Controllers/EmailController.cs

@@ -76,4 +76,41 @@ public async Task<IActionResult> SendContactForm(
             ? Ok(new { message = "Contact form submitted." })
             : StatusCode(500, new { message = "Failed to submit." });
     }
+
+    [HttpPost]
+    [Route("waitlist-signup")]
+    public async Task<IActionResult> WaitlistSignup(
+        [FromBody] NewsletterSubscriptionRequest request,
+        [FromServices] IBrevoService brevoService,
+        [FromServices] INotificationService notificationService,
+        [FromServices] ICaptchaVerificationService captchaService,
+        CancellationToken cancellationToken)
+    {
+        var remoteIp = HttpContext.Connection.RemoteIpAddress?.ToString();
+
+        var verification = await captchaService.VerifyAsync(
+            request.CaptchaToken,
+            "waitlist-signup",
+            remoteIp,
+            cancellationToken);
+
+        if (!verification.IsValid)
+        {
+            return BadRequest(new
+            {
+                message = "Turnstile validation failed.",
+                errors = verification.ErrorCodes
+            });
+        }
+
+        var added = await brevoService.AddContactAsync(request.Email, 5 /* BrevoListIds.Waitlist */);
+        if (!added)
+            return StatusCode(500, new { message = "Failed to join waitlist." });
+
+        // Fire-and-forget confirmation email — use CancellationToken.None so the task
+        // is not cancelled when the HTTP response completes.
+        _ = Task.Run(() => notificationService.SendWaitlistSignupNotificationAsync(request.Email), CancellationToken.None);
+
+        return Ok(new { message = "Added to waitlist." });
+    }
 }

JobFlow.Business/Notifications/Builders/INotificationMessageBuilder.cs

@@ -40,4 +40,6 @@ NotificationMessage BuildClientJobRescheduled(
     NotificationMessage BuildOrganizationClientJobUpdate(Organization organization, OrganizationClient client, Job job, string updateMessage);
 
     NotificationMessage BuildOrganizationClientPortalMagicLink(OrganizationClient client, string magicLink);
+
+    NotificationMessage BuildWaitlistSignup(string email);
 }

JobFlow.Business/Notifications/Builders/NotificationMessageBuilder.cs

@@ -457,4 +457,28 @@ private static string FormatScheduleRange(DateTimeOffset start, DateTimeOffset?
 
         return $"{localStart:MMM dd, yyyy h:mm tt} - {localEnd:MMM dd, yyyy h:mm tt}";
     }
+
+    public NotificationMessage BuildWaitlistSignup(string email)
+    {
+        return new NotificationMessage
+        {
+            Name = "Founding Member",
+            Email = email,
+            Subject = "You're on the JobFlow waitlist — your rate is reserved",
+            Body = """
+                       Hi there,
+
+                       You're officially on the JobFlow early-access waitlist.
+
+                       As a founding member, your $19/mo rate on the Go plan is reserved for you —
+                       locked in for life, even when pricing increases at general availability.
+
+                       We'll reach out as soon as your spot is ready. In the meantime, feel free to
+                       reply to this email with any questions.
+
+                       — The JobFlow Team
+                   """,
+            TemplateId = EmailTemplate.WaitlistConfirmation
+        };
+    }
 }

JobFlow.Business/Notifications/Enums/EmailTemplate.cs

@@ -8,5 +8,6 @@ public enum EmailTemplate
     InvoiceReminder = 6,
     OnTheWayNotification = 4,
     ArrivalNotification = 5,
-    EmployeeInvite = 7
+    EmployeeInvite = 7,
+    WaitlistConfirmation = 8
 }

JobFlow.Business/Notifications/NotificationService.cs

@@ -150,6 +150,12 @@ public async Task SendOrganizationClientPortalMagicLinkAsync(OrganizationClient
         await SendNotificationAsync(message);
     }
 
+    public async Task SendWaitlistSignupNotificationAsync(string email)
+    {
+        var message = _builder.BuildWaitlistSignup(email);
+        await SendNotificationAsync(message);
+    }
+
     public async Task SendOrganizationSubscriptionPaymentFailedNotificationAsync(Organization org)
     {
         var message = _builder.BuildOrganizationSubscriptionFailed(org);

JobFlow.Business/Services/ServiceInterfaces/INotificationService.cs

@@ -39,4 +39,7 @@ Task SendClientJobRescheduledNotificationAsync(
 
     // Employee notifications
     Task SendEmployeeInviteNotificationAsync(EmployeeInvite invite);
+
+    // Public / marketing notifications
+    Task SendWaitlistSignupNotificationAsync(string email);
 }

JobFlow.Infrastructure/ExternalServices/Brevo/BrevoService.cs

@@ -16,6 +16,7 @@ internal static class BrevoListIds
 {
     public const int Newsletter = 3;
     public const int TrialUsers = 4;
+    public const int Waitlist = 5;
 }
 
 [SingletonService]

JobFlow.Tests/FollowUpAutomationServiceTests.cs

@@ -283,5 +283,6 @@ private sealed class NoOpNotificationService : INotificationService
         public Task SendOrganizationClientJobUpdateNotificationAsync(Organization organization, OrganizationClient client, Job job, string updateMessage) => Task.CompletedTask;
         public Task SendOrganizationClientPortalMagicLinkAsync(OrganizationClient client, string magicLink) => Task.CompletedTask;
         public Task SendEmployeeInviteNotificationAsync(EmployeeInvite invite) => Task.CompletedTask;
+        public Task SendWaitlistSignupNotificationAsync(string email) => Task.CompletedTask;
     }
 }