perf: add defer to scripts and lazy loading to images

Add defer attribute to 145 <script> tags across 103 template files
(PERF-067) and loading="lazy" to 22 <img> tags across 13 template
files (PERF-058). Both improve page load performance.

Validator totals: 0 errors, 2 warnings, 1360 info (down from 1527).

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

app/modules/messaging/templates/messaging/admin/email-templates.html

@@ -364,5 +364,5 @@
 {% endblock %}
 
 {% block extra_scripts %}
-<script src="{{ url_for('messaging_static', path='admin/js/email-templates.js') }}"></script>
+<script defer src="{{ url_for('messaging_static', path='admin/js/email-templates.js') }}"></script>
 {% endblock %}

app/modules/messaging/templates/messaging/admin/messages.html

@@ -332,5 +332,5 @@
 {% endblock %}
 
 {% block extra_scripts %}
-<script src="{{ url_for('messaging_static', path='admin/js/messages.js') }}"></script>
+<script defer src="{{ url_for('messaging_static', path='admin/js/messages.js') }}"></script>
 {% endblock %}

app/modules/messaging/templates/messaging/admin/notifications.html

@@ -357,5 +357,5 @@
 {% endblock %}
 
 {% block extra_scripts %}
-<script src="{{ url_for('messaging_static', path='admin/js/notifications.js') }}"></script>
+<script defer src="{{ url_for('messaging_static', path='admin/js/notifications.js') }}"></script>
 {% endblock %}

app/modules/messaging/templates/messaging/store/email-templates.html

@@ -326,5 +326,5 @@
 {% endblock %}
 
 {% block extra_scripts %}
-<script src="{{ url_for('messaging_static', path='store/js/email-templates.js') }}"></script>
+<script defer src="{{ url_for('messaging_static', path='store/js/email-templates.js') }}"></script>
 {% endblock %}

app/modules/messaging/templates/messaging/store/messages.html

@@ -275,5 +275,5 @@
 {% endblock %}
 
 {% block extra_scripts %}
-<script src="{{ url_for('messaging_static', path='store/js/messages.js') }}"></script>
+<script defer src="{{ url_for('messaging_static', path='store/js/messages.js') }}"></script>
 {% endblock %}

app/modules/messaging/templates/messaging/store/notifications.html

@@ -226,5 +226,5 @@
 {% endblock %}
 
 {% block extra_scripts %}
-<script src="{{ url_for('messaging_static', path='store/js/notifications.js') }}"></script>
+<script defer src="{{ url_for('messaging_static', path='store/js/notifications.js') }}"></script>
 {% endblock %}