Enhance timeline and movement flow UI; add fetched painting images.

Timeline: era and historical-event click-to-zoom, event markers from historical-events.ts. Movement flow: shared zoom/pan, viewport-fit layout, curved lineage streams, hover-to-reveal artist lifespans on stacked lanes. Docs updated. Includes batch-fetched paintings and regenerated thumbs.
Co-authored-by: Cursor <cursoragent@cursor.com>

client/src/pages/HomePage.tsx

@@ -202,7 +202,7 @@ export default function HomePage() {
         <div className="home-page">
           <header className="site-header">
             <h1>Virtual Art Gallery</h1>
-            <p className="site-subtitle">Explore the flowing connections of art history</p>
+            <p className="site-subtitle">Watch art movements branch forward through time — each flowing from what came before</p>
           </header>
 
           <Timeline
@@ -217,15 +217,20 @@ export default function HomePage() {
           {error && <div className="error-banner">{error}</div>}
 
           {loading ? (
-            <div className="loading">Loading art history...</div>
+            <div className="loading home-movements-section">Loading art history...</div>
           ) : (
-            <MovementBands
-              movements={timelineData.movements}
-              artists={artists}
-              viewStart={viewStart}
-              viewEnd={viewEnd}
-              onArtistClick={handleArtistClick}
-            />
+            <div className="home-movements-section">
+              <MovementBands
+                movements={timelineData.movements}
+                artists={artists}
+                viewStart={viewStart}
+                viewEnd={viewEnd}
+                absoluteMin={bounds.min}
+                absoluteMax={bounds.max}
+                onViewChange={handleViewChange}
+                onArtistClick={handleArtistClick}
+              />
+            </div>
           )}
         </div>
       )}