feat(developers): overhaul signup to auto-register SilverDESK accounts

Users now pick a password and get a SilverDESK account immediately on
submit. The form includes debounced username availability checking,
password fields with validation, and a post-submit link to SilverDESK.
The approval flow no longer creates a SilverDESK user (already exists)
and only provisions Mattermost + Mailcow.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

BlazorApp/Services/DeveloperApplicationService.cs

@@ -1,3 +1,5 @@
+using System.Net.Http.Headers;
+using System.Net.Http.Json;
 using System.Text;
 using System.Text.Json;
 using SilverLabs.Website.Models;
@@ -15,13 +17,54 @@ public class DeveloperApplicationService
         _logger = logger;
     }
 
-    public async Task<(bool Success, string Message)> SubmitApplicationAsync(DeveloperApplication application)
+    public async Task<bool> CheckUsernameAsync(string username)
     {
         try
         {
-            var ticketBody = FormatTicketBody(application);
+            var response = await _httpClient.GetAsync($"/api/auth/check-username/{Uri.EscapeDataString(username)}");
+            if (!response.IsSuccessStatusCode)
+                return false;
 
-            var payload = new
+            var result = await response.Content.ReadFromJsonAsync<JsonElement>();
+            return result.TryGetProperty("available", out var available) && available.GetBoolean();
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Error checking username availability for {Username}", username);
+            return false;
+        }
+    }
+
+    public async Task<(bool Success, string Message, string? Token)> SubmitApplicationAsync(DeveloperApplication application)
+    {
+        try
+        {
+            // 1. Register user on SilverDESK
+            var registerPayload = new
+            {
+                username = application.DesiredUsername,
+                email = application.Email,
+                password = application.Password,
+                fullName = application.FullName
+            };
+
+            var registerResponse = await _httpClient.PostAsJsonAsync("/api/auth/register", registerPayload);
+
+            if (!registerResponse.IsSuccessStatusCode)
+            {
+                var errorBody = await registerResponse.Content.ReadAsStringAsync();
+                _logger.LogError("SilverDESK registration failed: {StatusCode} - {Body}", registerResponse.StatusCode, errorBody);
+
+                var friendlyMessage = ParseRegistrationError(errorBody);
+                return (false, friendlyMessage, null);
+            }
+
+            var authResult = await registerResponse.Content.ReadFromJsonAsync<JsonElement>();
+            var token = authResult.GetProperty("token").GetString();
+
+            // 2. Create ticket using the user's own JWT
+            var ticketBody = FormatTicketBody(application);
+            var ticketPayload = new
             {
                 Subject = $"[Developer Program] {application.Role} Application - {application.FullName}",
                 Description = ticketBody,
@@ -29,28 +72,54 @@ public class DeveloperApplicationService
                 Category = "Developer Program"
             };
 
-            var json = JsonSerializer.Serialize(payload);
-            var content = new StringContent(json, Encoding.UTF8, "application/json");
+            var ticketRequest = new HttpRequestMessage(HttpMethod.Post, "/api/tickets");
+            ticketRequest.Headers.Authorization = new AuthenticationHeaderValue("Bearer", token);
+            ticketRequest.Content = JsonContent.Create(ticketPayload);
 
-            var response = await _httpClient.PostAsync("/api/tickets", content);
+            var ticketResponse = await _httpClient.SendAsync(ticketRequest);
 
-            if (response.IsSuccessStatusCode)
+            if (!ticketResponse.IsSuccessStatusCode)
             {
-                _logger.LogInformation("Developer application submitted for {Email} as {Role}", application.Email, application.Role);
-                return (true, "Application submitted successfully! We'll review it and get back to you soon.");
+                var errorBody = await ticketResponse.Content.ReadAsStringAsync();
+                _logger.LogError("Failed to create ticket: {StatusCode} - {Body}", ticketResponse.StatusCode, errorBody);
+                // User was created but ticket failed — still return success with a note
+                return (true, "Your account has been created, but we had trouble submitting your application ticket. Please log in to SilverDESK and create a support ticket.", token);
             }
 
-            var errorBody = await response.Content.ReadAsStringAsync();
-            _logger.LogError("Failed to create ticket: {StatusCode} - {Body}", response.StatusCode, errorBody);
-            return (false, "Something went wrong submitting your application. Please try again later.");
+            _logger.LogInformation("Developer application submitted for {Email} as {Role} — user registered and ticket created",
+                application.Email, application.Role);
+
+            return (true, "Application submitted successfully! Your SilverDESK account has been created.", token);
         }
         catch (Exception ex)
         {
             _logger.LogError(ex, "Error submitting developer application for {Email}", application.Email);
-            return (false, "Unable to connect to the application service. Please try again later.");
+            return (false, "Unable to connect to the application service. Please try again later.", null);
         }
     }
 
+    private static string ParseRegistrationError(string errorBody)
+    {
+        try
+        {
+            var error = JsonSerializer.Deserialize<JsonElement>(errorBody);
+            if (error.TryGetProperty("message", out var message))
+            {
+                var msg = message.GetString() ?? "";
+                if (msg.Contains("Username already exists", StringComparison.OrdinalIgnoreCase))
+                    return "That username is already taken. Please choose a different one.";
+                if (msg.Contains("Email already exists", StringComparison.OrdinalIgnoreCase))
+                    return "An account with that email already exists.";
+                if (msg.Contains("Password", StringComparison.OrdinalIgnoreCase))
+                    return msg;
+                return msg;
+            }
+        }
+        catch { }
+
+        return "Something went wrong creating your account. Please try again later.";
+    }
+
     private static string FormatTicketBody(DeveloperApplication app)
     {
         var sb = new StringBuilder();