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.css

@@ -1,8 +1,18 @@
 .home-page {
-  min-height: 100vh;
+  height: 100vh;
+  overflow: hidden;
+  display: flex;
+  flex-direction: column;
   background: linear-gradient(180deg, #0f0f1a 0%, #1a1a2e 40%, #16213e 100%);
 }
 
+.home-movements-section {
+  flex: 1;
+  min-height: 0;
+  display: flex;
+  flex-direction: column;
+}
+
 .gallery-session-suspended {
   position: fixed;
   inset: 0;
@@ -21,6 +31,7 @@
 .site-header {
   text-align: center;
   padding: 24px 16px 8px;
+  flex-shrink: 0;
 }
 
 .site-header h1 {
@@ -47,6 +58,10 @@
   font-size: 16px;
 }
 
+.home-page > .timeline-wrapper {
+  flex-shrink: 0;
+}
+
 .error-banner {
   margin: 16px;
   padding: 12px 16px;

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>
       )}