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/components/navigation.html

@@ -0,0 +1,23 @@
+<nav>
+    <div class="nav-container">
+        <a href="/" class="logo">Rant</a>
+        <div class="nav-links">
+            <a href="/">Feed</a>
+            <a href="/search">Search</a>
+            {% if current_user %}
+                <span>
+                    <a href="/profile/{{ current_user.id }}">Profile</a>
+                    <a href="/notifications">Notifications {% if notif_count > 0 %}<span style="color: var(--error);">({{ notif_count }})</span>{% endif %}</a>
+                </span>
+                <span>
+                    <a href="/logout" class="btn btn-secondary">Logout</a>
+                </span>
+            {% else %}
+                <span>
+                    <button class="btn btn-secondary" onclick="showModal('login')">Login</button>
+                    <button class="btn" onclick="showModal('register')">Sign Up</button>
+                </span>
+            {% endif %}
+        </div>
+    </div>
+</nav>