Replace panel tileKey with a direct color prop.

Drop theme panelTiles keys and the ArticleView update callback wiring.

src/theme/themes/default.js

@@ -1,6 +1,5 @@
 import { createTheme } from '@mui/material/styles';
 import { MAIN_BACKGROUND } from '../../colors';
-import { PANEL_TILE_KEYS } from '../panelTiles';
 
 const nav = {
   background: '#1a3533',
@@ -13,17 +12,6 @@ const nav = {
   itemActiveAccent: '#2dd4bf',
 };
 
-const panelTiles = {
-  [PANEL_TILE_KEYS.name]: '#ffffff',
-  [PANEL_TILE_KEYS.photo]: '#fde68a',
-  [PANEL_TILE_KEYS.stock]: '#bbf7d0',
-  [PANEL_TILE_KEYS.brand]: '#e9d5ff',
-  [PANEL_TILE_KEYS.identifiers]: '#e2e8f0',
-  [PANEL_TILE_KEYS.price]: '#bfdbfe',
-  [PANEL_TILE_KEYS.content]: '#99f6e4',
-  [PANEL_TILE_KEYS.lists]: '#fbcfe8',
-};
-
 export const defaultThemeId = 'default';
 
 export function createDefaultTheme() {
@@ -37,6 +25,5 @@ export function createDefaultTheme() {
       },
     },
     nav,
-    panelTiles,
   });
 }