Security hardening: env-based config, CSRF protection, secure code generation, plus presenter management and email communications system

- Move all credentials from hardcoded to .env with python-dotenv (add .env.example template and .gitignore)
- Add CSRF token generation and validation on all state-changing requests
- Replace random.choices with secrets.choice for all secure code generation
- Add session cookie security headers (HttpOnly, Secure, SameSite)
- Add presenter management: assign/remove presenters to breakout sessions, presenter QR scanning
- Add email communications system: templates per event, custom email sending, sent email tracking
- Add staff/organizer profile pages with staff code display
- New DB tables: event_email_templates, sent_emails, user_communications
- New DB columns: staff.reminder_count/reminder_dates, breakout_session_organizers.presenter_code
- Expand English translation strings across all new features

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

templates/attendee/attendees.html

@@ -11,8 +11,8 @@
             {% if event.location %}
                 <span class="event-location">{{ event.location }}</span>
             {% endif %}
-            {% if event.start_date %}
-                <span class="event-date">{{ event.start_date|format_date }}</span>
+            {% if event.start_time %}
+                <span class="event-date">{{ event.start_time|localized_date }}</span>
             {% endif %}
         </div>
         {% if event.description %}
@@ -42,11 +42,11 @@
                             {% if att.profile_picture %}
                                 <img src="{{ url_for('static', filename='uploads/' + att.profile_picture) }}" alt="Photo">
                             {% else %}
-                                <div class="no-photo">{{ att.first_name[0] }}{{ att.last_name[0] }}</div>
+                                <div class="no-photo"><span class="first-name">{{ att.first_name[0] }}</span><span class="last-name">{{ att.last_name[0] }}</span></div>
                             {% endif %}
                         </div>
                         <div class="attendee-info">
-                            <h3>{{ att.first_name }} {{ att.last_name }}</h3>
+                            <h3><span class="first-name">{{ att.first_name }}</span> <span class="last-name">{{ att.last_name }}</span></h3>
                             <p class="attendee-org">{{ att.organisation if att.organisation else '' }}</p>
                             <p class="attendee-role">{{ att.role if att.role else '' }}</p>
                             {% if att.introduction %}