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/components/Timeline.css

@@ -41,7 +41,7 @@
 
 .timeline-container {
   position: relative;
-  height: 72px;
+  height: 88px;
   cursor: grab;
   user-select: none;
   border: 1px solid rgba(201, 169, 110, 0.3);
@@ -67,6 +67,23 @@
   align-items: center;
   justify-content: center;
   overflow: hidden;
+  padding: 0;
+  border-top: none;
+  border-bottom: none;
+  cursor: pointer;
+  transition: filter 0.2s, box-shadow 0.2s;
+}
+
+.era-block:hover {
+  filter: brightness(1.15);
+  box-shadow: inset 0 0 0 1px rgba(255, 255, 255, 0.35);
+  z-index: 2;
+}
+
+.era-block:focus-visible {
+  outline: 2px solid #c9a96e;
+  outline-offset: -2px;
+  z-index: 2;
 }
 
 .era-label {
@@ -79,6 +96,102 @@
   pointer-events: none;
 }
 
+.timeline-events {
+  position: absolute;
+  inset: 0;
+  z-index: 4;
+  pointer-events: none;
+}
+
+.historical-event {
+  position: absolute;
+  padding: 0;
+  border: none;
+  background: none;
+  cursor: pointer;
+  pointer-events: auto;
+}
+
+.historical-event-point {
+  top: 0;
+  bottom: 0;
+  width: 0;
+  transform: translateX(-50%);
+}
+
+.historical-event-point .event-marker-line {
+  position: absolute;
+  top: 18px;
+  bottom: 22px;
+  left: 50%;
+  width: 2px;
+  transform: translateX(-50%);
+  background: linear-gradient(
+    180deg,
+    rgba(255, 210, 120, 0.95) 0%,
+    rgba(255, 180, 90, 0.75) 100%
+  );
+  box-shadow: 0 0 6px rgba(255, 190, 100, 0.45);
+}
+
+.historical-event-point::before {
+  content: '';
+  position: absolute;
+  top: 12px;
+  left: 50%;
+  width: 7px;
+  height: 7px;
+  transform: translateX(-50%) rotate(45deg);
+  background: rgba(255, 215, 130, 0.95);
+  border: 1px solid rgba(255, 240, 200, 0.8);
+  box-shadow: 0 0 4px rgba(255, 200, 100, 0.5);
+}
+
+.historical-event-span {
+  top: 20px;
+  bottom: 24px;
+  background: rgba(180, 70, 55, 0.22);
+  border-left: 2px solid rgba(255, 150, 110, 0.65);
+  border-right: 2px solid rgba(255, 150, 110, 0.65);
+  border-radius: 2px;
+}
+
+.historical-event-span:hover,
+.historical-event-point:hover .event-marker-line {
+  filter: brightness(1.2);
+}
+
+.historical-event:focus-visible {
+  outline: 2px solid #e8c878;
+  outline-offset: 1px;
+}
+
+.event-label {
+  position: absolute;
+  top: 2px;
+  left: 50%;
+  transform: translateX(-50%);
+  max-width: 120px;
+  padding: 1px 5px;
+  font-family: 'Georgia', serif;
+  font-size: 9px;
+  font-weight: 600;
+  line-height: 1.2;
+  color: rgba(255, 235, 200, 0.95);
+  background: rgba(20, 16, 28, 0.72);
+  border: 1px solid rgba(255, 200, 120, 0.35);
+  border-radius: 3px;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+  text-shadow: 0 1px 2px rgba(0, 0, 0, 0.9);
+  pointer-events: none;
+}
+
+.historical-event-span .event-label {
+  top: 1px;
+}
+
 .timeline-ticks {
   position: absolute;
   bottom: 0;