fix: update sidebar components for consistent styling and improved unread item display

- Changed text color for active and archived item counts in AllPrivateChatsSidebar and AllSharedChatsSidebar to use 'text-muted-foreground' for better visibility.
- Replaced Loader2 with a new Spinner component in InboxSidebar for a consistent loading indicator.
- Enhanced unread item count display in InboxSidebar to show zero when no unread items are present, improving user feedback.
- Adjusted styles for MoreHorizontal and ListFilter icons in InboxSidebar to align with the updated design system.

surfsense_web/components/ui/spinner.tsx

@@ -0,0 +1,35 @@
+import { cn } from "@/lib/utils";
+
+interface SpinnerProps {
+  /** Size of the spinner */
+  size?: "xs" | "sm" | "md" | "lg" | "xl";
+  /** Whether to hide the track behind the spinner arc */
+  hideTrack?: boolean;
+  /** Additional classes to apply */
+  className?: string;
+}
+
+const sizeClasses = {
+  xs: "h-3 w-3 border-[1.5px]",
+  sm: "h-4 w-4 border-2",
+  md: "h-6 w-6 border-2",
+  lg: "h-8 w-8 border-[3px]",
+  xl: "h-10 w-10 border-4",
+};
+
+export function Spinner({ size = "md", hideTrack = false, className }: SpinnerProps) {
+  return (
+    <div
+      role="status"
+      aria-label="Loading"
+      className={cn(
+        "animate-spin rounded-full",
+        hideTrack ? "border-transparent" : "border-current/20",
+        "border-t-current",
+        sizeClasses[size],
+        className
+      )}
+    />
+  );
+}
+