Add thumbnail image card to main Spark page and move sliders and tags to bottom

public/styles.css

@@ -995,6 +995,89 @@ body {
   gap: 1.15rem;
 }
 
+.spark-main-hero {
+  display: grid;
+  grid-template-columns: 240px 1fr;
+  gap: 1.15rem;
+  align-items: start;
+}
+
+@media (max-width: 720px) {
+  .spark-main-hero {
+    grid-template-columns: 1fr;
+  }
+}
+
+.spark-main-pitch-col {
+  display: flex;
+  flex-direction: column;
+  gap: 1rem;
+  min-width: 0;
+}
+
+.spark-main-thumb-card {
+  background: var(--bg-elevated);
+  border: 1px solid var(--border-strong);
+  border-radius: var(--radius-md);
+  padding: 0.6rem;
+  display: flex;
+  flex-direction: column;
+  gap: 0.5rem;
+}
+
+.spark-main-thumb-empty {
+  min-height: 210px;
+  align-items: center;
+  justify-content: center;
+  text-align: center;
+  border-style: dashed;
+}
+
+.spark-thumb-placeholder-icon {
+  font-size: 2rem;
+  opacity: 0.7;
+}
+
+.spark-main-thumb-img {
+  width: 100%;
+  aspect-ratio: 1 / 1;
+  object-fit: cover;
+  border-radius: var(--radius-sm);
+  background: #10131b;
+  cursor: zoom-in;
+  border: 1px solid var(--border-color);
+}
+
+.spark-main-thumb-strip {
+  display: flex;
+  gap: 0.35rem;
+  overflow-x: auto;
+  padding-bottom: 0.15rem;
+}
+
+.spark-mini-thumb {
+  width: 38px;
+  height: 38px;
+  object-fit: cover;
+  border-radius: 4px;
+  border: 2px solid transparent;
+  cursor: pointer;
+  opacity: 0.7;
+  transition: opacity 0.15s ease, border-color 0.15s ease;
+}
+
+.spark-mini-thumb:hover,
+.spark-mini-thumb.active {
+  opacity: 1;
+  border-color: var(--accent-primary);
+}
+
+.spark-main-thumb-actions {
+  display: flex;
+  gap: 0.35rem;
+  justify-content: space-between;
+}
+
 .field-group {
   display: flex;
   flex-direction: column;