Add PainterPalette integration, canonical DB schema, and influence UI fixes.

Integrate Inputs/PainterPalette.csv for artist metadata and influence links, add db/schema.sql with server/migrate.js, letterbox influence panel thumbnails, and refresh Titian/Pontormo images.

Co-authored-by: Cursor <cursoragent@cursor.com>

Documentation/API.md

@@ -145,7 +145,8 @@ Full artist profile for the bio page and 3D gallery entry.
     "bio_full": "Full Wikipedia lead section…",
     "wikipedia_title": "Claude Monet",
     "checkup_checked": false,
-    "checkup_fixed": false
+    "checkup_fixed": false,
+    "palette_metadata": { "nationality": "French", "styles": "Impressionism, …", "source": "PainterPalette.csv", ... }
   },
   "periods": [ { "id": 1, "name": "Milan Period", "start_year": 1482, "end_year": 1499, ... } ],
   "paintings": [ { "id": 10, "title": "...", "year": 1498, "image_path": "...", "thumbnail_path": "...", "wikipedia_title": "...", "has_influence_links": true, "checkup_checked": false, "checkup_fixed": false, ... } ]
@@ -162,7 +163,7 @@ Each painting includes:
 
 Populate biographies with `npm run fetch-artist-bios` (see [data-and-images.md](data-and-images.md)).
 
-Artist objects also include `checkup_checked` and `checkup_fixed` (same semantics as paintings; gold portrait border when reviewed). Run `npm run migrate:artist-checkup-flags` on existing databases.
+Artist objects also include `checkup_checked` and `checkup_fixed` (same semantics as paintings; gold portrait border when reviewed). After `npm run import-painter-palette`, **`palette_metadata`** holds PainterPalette enrichment (nationality, styles, occupations, raw influence fields, etc.). Run `npm run migrate:artist-checkup-flags` and `npm run migrate:artist-palette` on existing databases.
 
 ---
 
@@ -361,6 +362,8 @@ Painting detail with influence graph neighbours.
 
 Both **`influencedBy`** and **`influenced`** are read from **`painting_influence_sources`** only (one row per edge). Painting-type sources appear in *Influenced By* when they are predecessors; in *Influenced* when this painting is the source of a later work. Artist and movement sources appear only in *Influenced By*. The legacy `painting_influences` table is not merged into these responses — it mirrors painting edges for scripts only.
 
+In the UI, side-panel thumbnails use the painting’s local image with **letterboxing** (`object-fit: contain`) so the full composition is visible. Click a thumbnail to open that work’s detail view.
+
 ---
 
 ## `GET /api/paintings/:id/image`