feat(admin): design system audit fixes

- Add CSS design tokens for consistency (--admin-danger-hover, --admin-accent-dot, shadow-md warm tone)
- Replace unicode icons with inline SVG (⋮, ✕, ▼, ▶)
- Consolidate duplicate PageHeader/AdminPageHeader components
- Standardize border-radius (rounded-xl → rounded-lg for ViewModeTabs)
- Remove hardcoded brand UUID in products page
- Replace hardcoded bg-red-600 with CSS variables in delete buttons
- Add AdminButton, AdminFilterTabs, AdminSearchInput, PageHeader design system components
- Fix GlassModal and AdminModal close button styling
- Remove duplicate 'New Lot' button on Route Trace dashboard

src/components/admin/ProductTableClient.tsx

@@ -224,7 +224,9 @@ function ProductRowBase({
             }}
             className="rounded-lg px-2 py-1.5 text-xs text-stone-400 hover:text-stone-600 hover:bg-stone-100 transition-colors"
           >
-            ⋮
+            <svg className="h-4 w-4" fill="currentColor" viewBox="0 0 20 20">
+              <circle cx="10" cy="4" r="1.5"/><circle cx="10" cy="10" r="1.5"/><circle cx="10" cy="16" r="1.5"/>
+            </svg>
           </button>
 
           {openMenu === product.id && (