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/data/movement-lineage.ts

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+/**
+ * Documented art-historical movement lineage (predecessor → successor).
+ * Sources: Met Museum essays, TheArtStory, Sotheby's movement guides.
+ *
+ * Multiple parents are allowed (e.g. Post-Impressionism feeding several modern paths).
+ */
+export const MOVEMENT_LINEAGE: ReadonlyArray<readonly [parent: string, child: string]> = [
+  // Classical & medieval
+  ['Ancient Greek & Roman', 'Byzantine'],
+  ['Byzantine', 'Gothic'],
+
+  // Renaissance chain
+  ['Gothic', 'Early Renaissance'],
+  ['Early Renaissance', 'High Renaissance'],
+  ['Northern Renaissance', 'Early Renaissance'],
+  ['High Renaissance', 'Mannerism'],
+  ['Mannerism', 'Baroque'],
+
+  // 17th–19th century
+  ['Baroque', 'Rococo'],
+  ['Rococo', 'Neoclassicism'],
+  ['Neoclassicism', 'Romanticism'],
+  ['Romanticism', 'Realism'],
+  ['Romanticism', 'Impressionism'], // Turner, Delacroix → light and atmosphere
+  ['Realism', 'Impressionism'],
+
+  // Modern origins (Met / ArtStory: Impressionism → Post-Impressionism → …)
+  ['Impressionism', 'Post-Impressionism'],
+  ['Post-Impressionism', 'Symbolism'],
+  ['Post-Impressionism', 'Fauvism'],
+  ['Post-Impressionism', 'Expressionism'],
+  ['Post-Impressionism', 'Cubism'], // Cézanne's structure → Picasso/Braque
+  ['Symbolism', 'Art Nouveau'],
+  ['Fauvism', 'Cubism'], // Braque, Matisse → geometric turn
+  ['Cubism', 'Futurism'],
+  ['Cubism', 'Suprematism'],
+  ['Cubism', 'Constructivism'],
+  ['Expressionism', 'Abstract Expressionism'],
+
+  // Avant-garde 20th century
+  ['Dada', 'Surrealism'],
+  ['Surrealism', 'Abstract Expressionism'],
+  ['Abstract Expressionism', 'Pop Art'],
+];
+
+export function lineageParentsByName(childName: string): string[] {
+  return MOVEMENT_LINEAGE.filter(([, child]) => child === childName).map(([parent]) => parent);
+}
+
+export function lineageChildrenByName(parentName: string): string[] {
+  return MOVEMENT_LINEAGE.filter(([parent]) => parent === parentName).map(([, child]) => child);
+}