Add UI interaction and component standards for Gallery screens.

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

.cursor/rules/ui-interaction-standards.mdc

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+---
+description: Gallery UI interaction and component standards for client screens
+globs: client/src/**/*.{tsx,css}
+alwaysApply: false
+---
+
+# UI interaction standards
+
+Follow [Documentation/ui-interaction-and-component-standards.md](Documentation/ui-interaction-and-component-standards.md) (MUST / SHOULD / MAY). Do not invent a second nav, toast, or CSS framework.
+
+## MUST
+
+- Drill-down via `HomePage` `View` state. Nested screens get an explicit Back; do not rely on the browser Back button.
+- **Back to Timeline** → `goToTimelineHome()` (clears hall, resets year range). **Back to Gallery** → same hall session (camera/wing kept).
+- Hide actions the user cannot `can()`; do not leave buttons that 403.
+- Visitor chrome strings in `locales/{en,ru}`. Movement colours via `utils/movementColor.ts`. Timeline zoom/pan via `utils/timelineView.ts`.
+- Loading: `GalleryLoadingMarker`. Errors/empty states: visible copy, not a blank canvas.
+- Modals: `role="dialog"`, visible close, Escape. No nested modals. Destructive actions confirm first.
+- Colocated CSS; museum gold `#c9a96e` / navy `/ Georgia`. No MUI/Ant Design.
+
+## SHOULD
+
+- Reuse `CatalogSearchBar`, `CuratorLoginModal`, `ArtistFilterModal`, `PaintingLightbox`, `DebugSearchResultsModal`, `DebugUploadButton`.
+- Curator filters above the table; expensive work behind an explicit button.
+- Update the standards doc when changing Back, search, layout query, or loading behaviour.