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/DoctorFormPage.tsx

@@ -429,7 +429,7 @@ export default function DoctorFormPage() {
             <button type="submit" disabled={createMut.isPending} className="cp-btn-primary" style={{ minWidth: 140 }}>
               {createMut.isPending ? (
                 <span style={{ display: 'flex', alignItems: 'center', gap: 8 }}>
-                  <span style={{ width: 16, height: 16, border: '2px solid rgba(255,255,255,.3)', borderTopColor: '#fff', borderRadius: '50%', animation: 'spin .7s linear infinite', flexShrink: 0 }} />
+                  <span style={{ width: 16, height: 16, border: '2px solid rgba(255,255,255,.3)', borderTopColor: 'var(--surface)', borderRadius: '50%', animation: 'spin .7s linear infinite', flexShrink: 0 }} />
                   در حال ذخیره...
                 </span>
               ) : (