Implement comprehensive dark/light mode overhaul for admin panel

- Refactor color palette in `ui-design-spec.md` to utilize CSS variables exclusively, eliminating fixed hex values and Tailwind utility classes.
- Complete dark mode implementation in `uiStore.ts`, ensuring proper theme application via `applyTheme()` and `applyBrand()`.
- Create `admin-theme-dark-light-audit.md` to document the transition process, outlining issues with inline styles and fixed colors.
- Introduce `theme-tokens.test.ts` to enforce rules against fixed hex colors and ensure compliance with the design system.
- Update various components and styles to replace inline styles and fixed colors with CSS variables, ensuring consistent theming across light and dark modes.
- Ensure all changes maintain visual integrity in both light and dark modes, with a focus on accessibility and contrast standards.

assets/admin/pages/BlogFormPage.tsx

@@ -142,7 +142,7 @@ export default function BlogFormPage() {
               <div>
                 <label>عنوان مقاله *</label>
                 <input {...register('title')} placeholder="عنوان جذاب بنویسید..." className="cp-input h-11" />
-                {errors.title && <p className="text-red-500 text-xs mt-1">{errors.title.message}</p>}
+                {errors.title && <p className="text-[var(--danger)] text-xs mt-1">{errors.title.message}</p>}
               </div>
 
               <div>
@@ -170,7 +170,7 @@ export default function BlogFormPage() {
                     </div>
                   )}
                 />
-                {errors.body && <p className="text-red-500 text-xs mt-1">{errors.body.message}</p>}
+                {errors.body && <p className="text-[var(--danger)] text-xs mt-1">{errors.body.message}</p>}
               </div>
             </div>