Add catalog search on timeline header and fix Back to Timeline navigation.

Public GET /api/search over artists, movements, and paintings with a debounced header bar on the timeline; Back to Timeline resets zoom and gallery session.

Co-authored-by: Cursor <cursoragent@cursor.com>

client/src/components/PaintingDetail.tsx

@@ -12,6 +12,7 @@ import './GalleryLoadingMarker.css';
 interface Props {
   data: PaintingDetail;
   artistPaintings?: Painting[];
+  backLabel?: string;
   onBack: () => void;
   onPaintingClick: (paintingId: number) => void;
   onCatalogNavigate: (paintingId: number) => void;
@@ -191,6 +192,7 @@ function InfluenceCard({
 export default function PaintingDetailView({
   data,
   artistPaintings = [],
+  backLabel = '← Back to Gallery',
   onBack,
   onPaintingClick,
   onCatalogNavigate,
@@ -457,7 +459,7 @@ export default function PaintingDetailView({
         />
       )}
       <header className="painting-header">
-        <button className="back-btn" onClick={onBack}>← Back to Gallery</button>
+        <button className="back-btn" onClick={onBack}>{backLabel}</button>
         <div className="painting-title-block">
           <h1>{painting.title}</h1>
           <p className="painting-meta">