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/auth/reset_password.html

@@ -10,11 +10,11 @@
         <form method="POST" action="{{ url_for('reset_password', token=token) }}">
             <div class="form-group">
                 <label for="password">{{ 'new_password'|t }}</label>
-                <input type="password" id="password" name="password" required minlength="6">
+                <input type="password" id="password" name="password" required minlength="8">
             </div>
             <div class="form-group">
                 <label for="confirm_password">{{ 'confirm_password'|t }}</label>
-                <input type="password" id="confirm_password" name="confirm_password" required minlength="6">
+                <input type="password" id="confirm_password" name="confirm_password" required minlength="8">
             </div>
 
             <button type="submit" class="btn btn-primary btn-block">{{ 'reset_password'|t }}</button>