Add privacy toggle to blur media on generate and gallery pages

- Add "Hide Media" / "Show Media" button to both sections
- Blur images and videos when privacy mode is active
- Persist privacy preference in localStorage per section

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/public/css/style.css

@@ -666,3 +666,29 @@ body {
         text-align: center;
     }
 }
+
+/* Privacy Mode */
+.privacy-toggle.active {
+    background: var(--primary);
+    color: white;
+}
+
+.privacy-mode .preview-image,
+.privacy-mode .output-video,
+.privacy-mode .gallery-item-media video,
+.privacy-mode .gallery-item-media img {
+    filter: blur(20px);
+    transition: filter 0.3s ease;
+}
+
+.privacy-mode .gallery-item-media::after {
+    content: 'Hidden';
+    position: absolute;
+    top: 50%;
+    left: 50%;
+    transform: translate(-50%, -50%);
+    color: white;
+    font-weight: 500;
+    text-shadow: 0 1px 3px rgba(0,0,0,0.5);
+    pointer-events: none;
+}