feat(developers): simplify timezone dropdown and make email optional

Replace 100+ raw system timezones with curated list of 26 major zones
with browser auto-detection via Intl API. Remove email requirement since
applicants receive a @silverlabs.uk address — fallback to username@silverlabs.uk
when no personal email is provided.

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

BlazorApp/Services/DeveloperApplicationService.cs

@@ -48,11 +48,16 @@ public class DeveloperApplicationService
     {
         try
         {
+            // Use silverlabs.uk address when no personal email provided
+            var effectiveEmail = string.IsNullOrWhiteSpace(application.Email)
+                ? $"{application.DesiredUsername}@silverlabs.uk"
+                : application.Email.Trim();
+
             // 1. Register user on SilverDESK
             var registerPayload = new
             {
                 username = application.DesiredUsername,
-                email = application.Email,
+                email = effectiveEmail,
                 password = application.Password,
                 fullName = application.FullName
             };
@@ -111,7 +116,7 @@ public class DeveloperApplicationService
                     userId,
                     ticketId,
                     fullName = application.FullName,
-                    email = application.Email,
+                    email = effectiveEmail,
                     desiredUsername = application.DesiredUsername,
                     timezone = application.Timezone,
                     appliedRole = application.Role.ToString(),
@@ -126,29 +131,29 @@ public class DeveloperApplicationService
 
                 if (appResponse.IsSuccessStatusCode)
                 {
-                    _logger.LogInformation("DeveloperApplication record created for {Email}", application.Email);
+                    _logger.LogInformation("DeveloperApplication record created for {Email}", effectiveEmail);
                 }
                 else
                 {
                     var appError = await appResponse.Content.ReadAsStringAsync();
                     _logger.LogWarning("Failed to create DeveloperApplication record for {Email}: {StatusCode} - {Body}",
-                        application.Email, appResponse.StatusCode, appError);
+                        effectiveEmail, appResponse.StatusCode, appError);
                 }
             }
             catch (Exception ex)
             {
                 _logger.LogWarning(ex, "Failed to create DeveloperApplication record for {Email} — user and ticket were created successfully",
-                    application.Email);
+                    effectiveEmail);
             }
 
             _logger.LogInformation("Developer application submitted for {Email} as {Role} — user registered and ticket created",
-                application.Email, application.Role);
+                effectiveEmail, 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);
+            _logger.LogError(ex, "Error submitting developer application for {Username}", application.DesiredUsername);
             return (false, "Unable to connect to the application service. Please try again later.", null);
         }
     }
@@ -177,12 +182,16 @@ public class DeveloperApplicationService
 
     private static string FormatTicketBody(DeveloperApplication app)
     {
+        var effectiveEmail = string.IsNullOrWhiteSpace(app.Email)
+            ? $"{app.DesiredUsername}@silverlabs.uk"
+            : app.Email.Trim();
+
         var sb = new StringBuilder();
         sb.AppendLine("## Developer Program Application");
         sb.AppendLine();
         sb.AppendLine($"**Role:** {app.Role}");
         sb.AppendLine($"**Full Name:** {app.FullName}");
-        sb.AppendLine($"**Email:** {app.Email}");
+        sb.AppendLine($"**Email:** {effectiveEmail}");
         sb.AppendLine($"**Desired Username:** {app.DesiredUsername}");
         sb.AppendLine($"**Timezone:** {app.Timezone}");
         sb.AppendLine();