feat: add dynamic header hiding on scroll and back-to-top button

- Hide header when scrolling down, show when scrolling up
- Smooth transition animations for header hide/show
- Floating back-to-top button in bottom right corner
- Button appears after 300px scroll
- Circular button with arrow icon and smooth animations
- Mobile-responsive sizing for back-to-top button
- Both features excluded from print view

static/css/main.css

@@ -1660,3 +1660,68 @@ html {
         display: none !important;
     }
 }
+
+/* ========================================
+   Scroll Direction - Hide/Show Header
+   ======================================== */
+
+/* Add smooth transition to header elements */
+.action-bar,
+.navigation-menu {
+    transition: transform 0.3s ease-in-out;
+}
+
+/* Hide header when scrolling down */
+.action-bar.header-hidden {
+    transform: translateY(-100%);
+}
+
+.navigation-menu.header-hidden {
+    transform: translateY(-100%);
+}
+
+/* ========================================
+   Back to Top Button
+   ======================================== */
+
+.back-to-top {
+    position: fixed;
+    bottom: 2rem;
+    right: 2rem;
+    width: 50px;
+    height: 50px;
+    background: var(--black-bar);
+    color: white;
+    border: none;
+    border-radius: 50%;
+    cursor: pointer;
+    display: flex;
+    align-items: center;
+    justify-content: center;
+    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
+    z-index: 99;
+    transition: all 0.3s ease;
+    opacity: 0.9;
+}
+
+.back-to-top:hover {
+    opacity: 1;
+    transform: translateY(-3px);
+    box-shadow: 0 6px 16px rgba(0, 0, 0, 0.4);
+    background: #3a3a3a;
+}
+
+.back-to-top:active {
+    transform: translateY(-1px);
+    box-shadow: 0 3px 10px rgba(0, 0, 0, 0.3);
+}
+
+/* Mobile adjustments */
+@media (max-width: 768px) {
+    .back-to-top {
+        bottom: 1.5rem;
+        right: 1.5rem;
+        width: 45px;
+        height: 45px;
+    }
+}