Refactor AdminSettings into modular components

Split 1123-line monolithic AdminSettings.tsx into 11 modules:

Components:
- icons.tsx (85 lines) - All SVG icons
- Toggle.tsx (21 lines) - Reusable toggle component
- SettingInput.tsx (89 lines) - Text/select input for settings
- SettingRow.tsx (104 lines) - Single setting card
- BrandingTab.tsx (212 lines) - Logo, name, animation settings
- ThemeTab.tsx (277 lines) - Theme presets and custom colors
- FavoritesTab.tsx (59 lines) - Starred settings display
- SettingsTab.tsx (144 lines) - Accordion categories view

Utilities:
- constants.ts (55 lines) - MENU_SECTIONS, THEME_PRESETS
- utils.ts (35 lines) - formatSettingKey, stripHtml
- index.ts (13 lines) - Barrel exports

Result: AdminSettings.tsx reduced from 1123 to 251 lines

src/components/admin/FavoritesTab.tsx

@@ -0,0 +1,59 @@
+import { useTranslation } from 'react-i18next'
+import { useMutation, useQueryClient } from '@tanstack/react-query'
+import { SettingDefinition, adminSettingsApi } from '../../api/adminSettings'
+import { StarIcon } from './icons'
+import { SettingRow } from './SettingRow'
+
+interface FavoritesTabProps {
+  settings: SettingDefinition[]
+  isFavorite: (key: string) => boolean
+  toggleFavorite: (key: string) => void
+}
+
+export function FavoritesTab({ settings, isFavorite, toggleFavorite }: FavoritesTabProps) {
+  const { t } = useTranslation()
+  const queryClient = useQueryClient()
+
+  const updateSettingMutation = useMutation({
+    mutationFn: ({ key, value }: { key: string; value: string }) => adminSettingsApi.updateSetting(key, value),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['admin-settings'] })
+    },
+  })
+
+  const resetSettingMutation = useMutation({
+    mutationFn: (key: string) => adminSettingsApi.resetSetting(key),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ['admin-settings'] })
+    },
+  })
+
+  if (settings.length === 0) {
+    return (
+      <div className="p-12 rounded-2xl bg-dark-800/30 border border-dark-700/30 text-center">
+        <div className="flex justify-center mb-4 text-dark-500">
+          <StarIcon filled={false} />
+        </div>
+        <p className="text-dark-400">{t('admin.settings.favoritesEmpty')}</p>
+        <p className="text-dark-500 text-sm mt-1">{t('admin.settings.favoritesHint')}</p>
+      </div>
+    )
+  }
+
+  return (
+    <div className="grid grid-cols-1 lg:grid-cols-2 xl:grid-cols-3 gap-4">
+      {settings.map((setting) => (
+        <SettingRow
+          key={setting.key}
+          setting={setting}
+          isFavorite={isFavorite(setting.key)}
+          onToggleFavorite={() => toggleFavorite(setting.key)}
+          onUpdate={(value) => updateSettingMutation.mutate({ key: setting.key, value })}
+          onReset={() => resetSettingMutation.mutate(setting.key)}
+          isUpdating={updateSettingMutation.isPending}
+          isResetting={resetSettingMutation.isPending}
+        />
+      ))}
+    </div>
+  )
+}