Add zoom/cell-size slider to grid viewer

Images and labels scale together with a range slider (40–300px).
Grid scrolls horizontally when cells exceed viewport width.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

public/style.css

@@ -1333,13 +1333,32 @@ nav {
 
 .grid-viewer-actions {
 	display: flex;
+	align-items: center;
 	gap: 0.5rem;
 	flex-shrink: 0;
 }
 
+.gv-zoom-label {
+	display: flex;
+	align-items: center;
+	gap: 0.4rem;
+	font-size: 0.8rem;
+	color: var(--text-dim);
+}
+
+.gv-zoom-label input[type=range] {
+	width: 100px;
+	accent-color: var(--accent);
+}
+
+.grid-cells-wrap {
+	overflow-x: auto;
+}
+
 .grid-cells {
 	display: grid;
 	gap: 4px;
+	min-width: max-content;
 }
 
 .grid-cell {