feat(admin): add orange rgb(241,119,50) as an exact brand-color option

Revert the earlier mis-scoped orange on the personalization panel and
instead expose rgb(241,119,50) as a selectable 'رنگ اصلی' swatch. When
picked it overrides --primary/-600/-700/-soft/-soft2/-ring inline with
exact hex, so every var(--primary) consumer across the whole admin
(buttons, active nav, rings) becomes that orange. Non-fixed hues keep
the oklch hue pipeline (inline overrides removed on switch).

- uiStore: BrandHue interface + optional fixed hex; shared applyBrand()
  helper handles fixed vs hue, dark-aware soft tints
- AdminLayout: reuse applyBrand() (no divergence with store)
- Topbar: swatch shows the exact fixed color
- tests: fixed-color apply, dark soft, and override-cleanup on switch

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

assets/admin/components/layout/AdminLayout.tsx

@@ -2,7 +2,7 @@ import React, { useEffect, useState } from 'react';
 import { Outlet } from 'react-router-dom';
 import Sidebar from './Sidebar';
 import Topbar from './Topbar';
-import { useUiStore } from '../../stores/uiStore';
+import { useUiStore, applyBrand } from '../../stores/uiStore';
 
 export default function AdminLayout() {
   const darkMode      = useUiStore((s) => s.darkMode);
@@ -17,8 +17,7 @@ export default function AdminLayout() {
     root.classList.toggle('dark', darkMode);
     root.setAttribute('data-theme', darkMode ? 'dark' : 'light');
     root.setAttribute('data-density', density);
-    root.style.setProperty('--brand-h', String(brandHue.h));
-    root.style.setProperty('--brand-c', String(brandHue.c));
+    applyBrand(root, brandHue, darkMode);
   }, [darkMode, density, brandHue]);
 
   return (

assets/admin/components/layout/Topbar.tsx

@@ -124,7 +124,7 @@ export default function Topbar({ onMobileMenuOpen }: { onMobileMenuOpen?: () =>
                       title={hue.name}
                       style={{
                         width: 40, height: 40, borderRadius: 10,
-                        background: `oklch(0.55 ${hue.c} ${hue.h})`,
+                        background: hue.fixed?.primary ?? `oklch(0.55 ${hue.c} ${hue.h})`,
                         border: brandHue.h === hue.h ? '3px solid var(--text)' : '3px solid transparent',
                         display: 'grid', placeItems: 'center', color: '#fff', cursor: 'pointer',
                       }}