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/NewSessionPage.tsx

@@ -54,10 +54,10 @@ export default function NewSessionPage() {
     <div className="fade-in" style={{ width: '100%' }}>
       {/* breadcrumb — tauri AddService header */}
       <div style={{ display: 'flex', justifyContent: 'flex-start', marginBottom: 30 }}>
-        <div className="dark:text-[#A1A1A1]" style={{ display: 'flex', alignItems: 'center', gap: 8, color: '#6B7280', fontSize: 12, padding: '0 16px' }}>
+        <div style={{ display: 'flex', alignItems: 'center', gap: 8, color: 'var(--text-2)', fontSize: 12, padding: '0 16px' }}>
           <div
             onClick={() => nav(-1)}
-            className="bg-white dark:bg-[#222433]"
+            className="bg-[var(--surface)]"
             style={{ display: 'flex', alignItems: 'center', gap: 4, padding: '6px 8px', borderRadius: 12, cursor: 'pointer' }}
           >
             <ArrowLeftPH style={{ width: 18, height: 18, rotate: '180deg' }} />
@@ -66,13 +66,13 @@ export default function NewSessionPage() {
           <ArrowLeftD />
           <span>پرونده</span>
           <ArrowLeftD />
-          <span className="dark:text-[#D7D8ED]" style={{ color: '#111827' }}>{patientName}</span>
+          <span style={{ color: 'var(--text)' }}>{patientName}</span>
         </div>
       </div>
 
       {/* card — tauri width 748 centered */}
       <div style={{ width: '100%', display: 'flex', justifyContent: 'center' }}>
-        <div className="bg-white dark:bg-[#222433]" style={{ width: 748, maxWidth: '100%', padding: 24 }}>
+        <div className="bg-[var(--surface)]" style={{ width: 748, maxWidth: '100%', padding: 24 }}>
           <div style={{ display: 'flex', justifyContent: 'flex-end', marginBottom: 8 }}>
             <button
               type="button"