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/appointments/TurnsTimeline.tsx

@@ -77,7 +77,7 @@ function EmptyCard({ slot, onBook }: { slot: TimelineSlot; onBook: (s: TimelineS
         cursor: isPast ? 'not-allowed' : 'pointer', opacity: isPast ? 0.7 : 1, minHeight: 76,
       }}
     >
-      <InnerTimes start={slot.start_time} end={slot.end_time} color={isPast ? '#9E9E9E' : cfg.dotColor} />
+      <InnerTimes start={slot.start_time} end={slot.end_time} color={isPast ? 'var(--text-3)' : cfg.dotColor} />
       <div style={{ flex: 1, display: 'flex', alignItems: 'center', justifyContent: 'center', gap: 6 }}>
         <span style={{ fontSize: 13.5, color: isPast ? 'var(--text-3)' : cfg.textColor, fontWeight: 500 }}>
           {isPast ? 'گذشته' : 'افزودن نوبت سریع'}
@@ -88,8 +88,8 @@ function EmptyCard({ slot, onBook }: { slot: TimelineSlot; onBook: (s: TimelineS
       {!isPast && (
         <span style={{
           display: 'inline-flex', alignItems: 'center', gap: 5, padding: '3px 10px', borderRadius: 99,
-          fontSize: 12, fontWeight: 700, color: cfg.textColor, background: `${cfg.dotColor}15`,
-          border: `1.5px solid ${cfg.dotColor}30`, whiteSpace: 'nowrap', alignSelf: 'flex-start',
+          fontSize: 12, fontWeight: 700, color: cfg.textColor, background: `color-mix(in srgb, ${cfg.dotColor} 8%, transparent)`,
+          border: `1.5px solid color-mix(in srgb, ${cfg.dotColor} 19%, transparent)`, whiteSpace: 'nowrap', alignSelf: 'flex-start',
         }}>
           <span style={{ width: 7, height: 7, borderRadius: '50%', background: cfg.dotColor }} />
           نوبت جدید