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>

Documentation/data-and-images.md

@@ -130,6 +130,31 @@ Each entry defines a later `work` influenced by an earlier `influencedBy` painti
 
 Extend the data file to add lineage chains (e.g. Giotto → Masaccio → Michelangelo → Manet → Picasso → Warhol). New bridge artists may include Géricault, Friedrich, Constable, Giorgione, Poussin, de Chirico, and Böcklin.
 
+## Movement lineage (frontend flow diagram)
+
+Separate from the painting influence graph, `client/src/data/movement-lineage.ts` lists **art-movement** predecessor→successor pairs used only by `MovementBands.tsx` to position streams and draw branch connectors (e.g. Impressionism → Post-Impressionism → Fauvism / Cubism / Expressionism).
+
+| Aspect | Detail |
+|--------|--------|
+| Storage | TypeScript module in the client — **not** a database table |
+| Format | `[parentMovementName, childMovementName]` tuples; names must match `art_movements.name` from the seed |
+| Multiple parents | Allowed (e.g. Post-Impressionism feeding several modern paths) |
+| Sources | Curator notes in the file reference Met essays, TheArtStory, and similar |
+
+To add or fix a branch, edit `MOVEMENT_LINEAGE` in that file and rebuild the client. No migration or API change is required.
+
+## Historical event markers (frontend timeline)
+
+`client/src/data/historical-events.ts` lists **world-history** markers shown on `Timeline.tsx` (French Revolution, World War I/II, etc.).
+
+| Aspect | Detail |
+|--------|--------|
+| Storage | TypeScript module in the client — **not** a database table |
+| Format | `{ id, name, startYear, endYear?, shortLabel? }` — omit `endYear` for a single-year pin |
+| Interaction | Click a marker to zoom the shared timeline/movement view to that period |
+
+Edit `HISTORICAL_EVENTS` and rebuild the client to extend the set.
+
 ## Batch image fetch
 
 `npm run fetch-images` (alias: `npm run search-missing-paintings`) runs `scripts/fetch-missing-images.js`. It searches multiple sources for paintings without local files:
@@ -152,13 +177,15 @@ Extend the data file to add lineage chains (e.g. Giotto → Masaccio → Michela
 ```bash
 npm run fetch-images                              # all missing, catalog order (~hours)
 npm run fetch-images -- --limit=50                # random sample of 50; 10s max per painting
-npm run fetch-images -- --limit=920               # random sample up to N missing works
+npm run fetch-images -- --limit=250               # random sample up to N (caps at current missing count)
 npm run fetch-images -- --limit=50 --max-wait=120 # slower, more thorough lookup per painting
 npm run fetch-images -- --artist="Albrecht Dürer" # one artist, catalog order
 npm run fetch-images -- --discover-only --limit=20   # fix wikipedia_title only
 npm run fetch-images -- --web-search-only --limit=50 # DuckDuckGo + Commons + multilingual Wikipedia
 ```
 
+Each run prints **`Missing local files: N`** at startup — that is the current count of catalogued paintings with no full-size or thumbnail file under `data/images/`. A painting counts as present if **either** file exists on disk.
+
 | Flag | Effect |
 |------|--------|
 | `--limit=N` | Process at most **N** paintings. Queue is a **random sample** of all works missing local files (not alphabetical). |
@@ -198,7 +225,7 @@ The 3D scene uses `galleryImageUrl()`, which never hits the on-demand API (remot
 
 When no image is available:
 
-- `/placeholder-portrait.svg` — timeline / movement band portraits
+- `/placeholder-portrait.svg` — timeline and movement-flow portraits
 - `/placeholder-art.svg` — paintings in lists and detail view
 - **3D gallery** — draped **canvas cover** inside the frame (`CanvasCover` in `VirtualGallery.tsx`); shown when there is no local file, the fetch failed, or the texture has not loaded yet