feat: add image search with Bing, DuckDuckGo, and Qwant engines

Three new image search engines:
- bing_images: Bing Images via RSS endpoint
- ddg_images: DuckDuckGo Images via VQD API
- qwant_images: Qwant Images via v3 search API

Frontend:
- Image grid layout with responsive columns
- image_item template with thumbnail, title, and source metadata
- Hover animations and lazy loading
- Grid activates automatically when category=images

Backend:
- category=images routes to image engines via planner
- Image engines registered in factory and engine allowlist
- extractImgSrc helper for parsing thumbnail URLs from HTML
- IsImageSearch flag on PageData for template layout switching

internal/views/static/css/kafka.css

@@ -952,6 +952,100 @@ footer a:hover {
   }
 }
 
+/* ============================================================
+   Image Results
+   ============================================================ */
+
+.image-grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
+  gap: 1rem;
+}
+
+.image-result {
+  display: block;
+  border-radius: var(--radius-sm);
+  overflow: hidden;
+  background: var(--bg-secondary);
+  border: 1px solid var(--border);
+  transition: transform 0.15s ease, box-shadow 0.15s ease;
+  text-decoration: none;
+  color: inherit;
+}
+
+.image-result:hover {
+  transform: translateY(-2px);
+  box-shadow: 0 4px 12px var(--shadow);
+}
+
+.image-result:focus-visible {
+  outline: 2px solid var(--accent);
+  outline-offset: 2px;
+}
+
+.image-thumb {
+  aspect-ratio: 1;
+  overflow: hidden;
+  background: var(--bg-tertiary);
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+
+.image-thumb img {
+  width: 100%;
+  height: 100%;
+  object-fit: cover;
+  display: block;
+  transition: transform 0.2s ease;
+}
+
+.image-result:hover .image-thumb img {
+  transform: scale(1.05);
+}
+
+.image-thumb.image-error img,
+.image-thumb.image-error {
+  display: none;
+}
+
+.image-placeholder {
+  font-size: 2rem;
+  opacity: 0.3;
+}
+
+.image-meta {
+  padding: 0.5rem;
+  min-height: 2.5rem;
+  display: flex;
+  flex-direction: column;
+  gap: 0.15rem;
+}
+
+.image-title {
+  font-size: 0.8rem;
+  font-weight: 500;
+  color: var(--text-primary);
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+.image-source {
+  font-size: 0.7rem;
+  color: var(--text-secondary);
+  overflow: hidden;
+  text-overflow: ellipsis;
+  white-space: nowrap;
+}
+
+@media (max-width: 480px) {
+  .image-grid {
+    grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
+    gap: 0.5rem;
+  }
+}
+
 /* ============================================================
    Infoboxes
    ============================================================ */