refactor: update styles in MembersDirectory and NewsletterArchive for consistency and improved theming

- Updated color classes to use CSS variables for better maintainability and theming.
- Refactored component styles in MembersDirectory.js to enhance visual consistency.
- Adjusted loading states and empty states in NewsletterArchive.js for improved user experience.
- Added new brand colors to tailwind.config.js for future use.

src/components/ui/tabs.jsx

@@ -21,7 +21,7 @@ const TabsTrigger = React.forwardRef(({ className, ...props }, ref) => (
   <TabsPrimitive.Trigger
     ref={ref}
     className={cn(
-      "inline-flex items-center justify-center whitespace-nowrap hover:bg-[#f1eef9] border-2 border-[#664fa3] rounded-2xl px-3 py-1 text-[#664fa3] text-sm font-medium ring-offset-background transition-all focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 disabled:pointer-events-none disabled:opacity-50 data-[state=active]:bg-foreground data-[state=active]:text-background data-[state=active]:border-foreground data-[state=active]:shadow",
+      "inline-flex items-center justify-center whitespace-nowrap hover:bg-var(--lavender-300) border-2 border-var(--purple-lavender) rounded-2xl px-3 py-1 text-var(--purple-lavender) text-sm font-medium ring-offset-background transition-all focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-2 disabled:pointer-events-none disabled:opacity-50 data-[state=active]:bg-foreground data-[state=active]:text-background data-[state=active]:border-foreground data-[state=active]:shadow",
       className
     )}
     {...props}