Add assignment dropdown on ticket creation and fix Discord webhook URLs

- Add APP_DOMAIN config for correct Discord webhook ticket links
- Add "Assign To" dropdown on create ticket form
- Update TicketModel.createTicket() to support assigned_to field
- Update documentation for APP_DOMAIN requirement

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.env.example

@@ -10,5 +10,13 @@ DB_NAME=ticketing_system
 # Discord Webhook (optional - for notifications)
 DISCORD_WEBHOOK_URL=
 
+# Application Domain (required for Discord webhook links)
+# Set this to your public domain (e.g., t.lotusguild.org)
+APP_DOMAIN=
+
+# Allowed Hosts for HTTP_HOST validation (comma-separated)
+# Include all domains that can access this application
+ALLOWED_HOSTS=localhost,127.0.0.1
+
 # Timezone (default: America/New_York)
 TIMEZONE=America/New_York