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/components/dashboard/TauriCharts.test.tsx

@@ -31,7 +31,7 @@ describe('TauriBarChart', () => {
   it('renders one bar per day of a full Jalali month', () => {
     const month: ChartPoint[] = Array.from({ length: 31 }, (_, i) => ({ label: String(i + 1), value: i % 5 }));
     const { container } = render(<TauriBarChart data={month} />);
-    expect(container.querySelectorAll('.bg-\\[\\#5559CE\\]')).toHaveLength(31);
+    expect(container.querySelectorAll('[class*="bg-[var(--primary)]"]')).toHaveLength(31);
   });
 
   /**
@@ -44,7 +44,7 @@ describe('TauriBarChart', () => {
     const month: ChartPoint[] = Array.from({ length: 31 }, (_, i) => ({ label: String(i + 1), value: i % 5 }));
     const { container } = render(<TauriBarChart data={month} />);
 
-    const bar = container.querySelector('.bg-\\[\\#5559CE\\]') as HTMLElement;
+    const bar = container.querySelector('[class*="bg-[var(--primary)]"]') as HTMLElement;
     // کسری از ستون، نه تمام آن — وگرنه میله‌ها بدون فاصله به هم می‌چسبند
     expect(bar.className).toMatch(/\bw-\[\d+%\]/);
     expect(bar.className.split(/\s+/)).not.toContain('w-full');