feat: add Jinja2 server-side rendering with template components and locust load testing

Introduce a full server-side rendering pipeline using Jinja2Templates, including base layout, navigation, modals, and rant card components. Add a classic.html static fallback page and a locustfile.py for load testing the new endpoints. Update main.py to mount static files, create template directories on startup, and add a format_time helper for relative timestamps.

templates/notifications.html

@@ -0,0 +1,15 @@
+{% extends 'base.html' %}
+
+{% block content %}
+<h2>Notifications</h2>
+{% if items %}
+    {% for notif in items %}
+    <div class="rant-card" onclick="window.location.href='/rant/{{ notif.rant_id }}';" style="cursor: pointer;">
+        <p><strong>{{ notif.username }}</strong> {% if notif.type == 'comment' %}commented on your rant{% else %}mentioned you{% endif %}</p>
+        <p style="color: var(--text-dim); font-size: 0.9rem;">{{ format_time(notif.created_time) }}</p>
+    </div>
+    {% endfor %}
+{% else %}
+    <p style="text-align: center; color: var(--text-dim); margin-top: 2rem;">No notifications</p>
+{% endif %}
+{% endblock %}