fix: improve dark mode compatibility and chart visibility

- Fix TopQuestionsChart with proper dark mode colors using CSS variables and shadcn/ui components
- Enhance ResponseTimeDistribution with thicker bars (maxBarSize: 60)
- Replace GeographicMap with dark/light mode compatible CartoDB tiles
- Add custom text selection background color with primary theme color
- Update all loading states to use proper CSS variables instead of hardcoded colors
- Fix dashboard layout background to use bg-background instead of bg-gray-100

components/ui/label.tsx

@@ -0,0 +1,26 @@
+"use client";
+
+import * as React from "react";
+import * as LabelPrimitive from "@radix-ui/react-label";
+import { cva, type VariantProps } from "class-variance-authority";
+
+import { cn } from "@/lib/utils";
+
+const labelVariants = cva(
+  "text-sm font-medium leading-none peer-disabled:cursor-not-allowed peer-disabled:opacity-70"
+);
+
+const Label = React.forwardRef<
+  React.ElementRef<typeof LabelPrimitive.Root>,
+  React.ComponentPropsWithoutRef<typeof LabelPrimitive.Root> &
+    VariantProps<typeof labelVariants>
+>(({ className, ...props }, ref) => (
+  <LabelPrimitive.Root
+    ref={ref}
+    className={cn(labelVariants(), className)}
+    {...props}
+  />
+));
+Label.displayName = LabelPrimitive.Root.displayName;
+
+export { Label };