feat(usage): redesign Usage Analytics with accurate token averages

- Fix token averaging: calculate over active hours/days only (not full period)
- Enable hourlyData query for all time ranges (not just 24h)
- Rename 'Usage Forecast' to 'Usage Averages' (real data, not projections)
- Add avg/request metric and active hours/days context
- Update terminology: Input/Output Tokens with info tooltips
- Add Estimated Cost stat card with per-model calculation
- Add quota warning alert banner when models exceed 80%
- Add ModelQuotaBar component with color thresholds

src/components/ui/alert.tsx

@@ -0,0 +1,49 @@
+import * as React from 'react';
+import { cva, type VariantProps } from 'class-variance-authority';
+
+import { cn } from '@/lib/utils';
+
+const alertVariants = cva(
+  'relative w-full rounded-lg border p-4 [&>svg~*]:pl-7 [&>svg+div]:translate-y-[-3px] [&>svg]:absolute [&>svg]:left-4 [&>svg]:top-4 [&>svg]:text-foreground',
+  {
+    variants: {
+      variant: {
+        default: 'bg-background text-foreground',
+        destructive:
+          'border-destructive/50 text-destructive dark:border-destructive [&>svg]:text-destructive',
+      },
+    },
+    defaultVariants: {
+      variant: 'default',
+    },
+  },
+);
+
+const Alert = React.forwardRef<
+  HTMLDivElement,
+  React.HTMLAttributes<HTMLDivElement> & VariantProps<typeof alertVariants>
+>(({ className, variant, ...props }, ref) => (
+  <div ref={ref} role="alert" className={cn(alertVariants({ variant }), className)} {...props} />
+));
+Alert.displayName = 'Alert';
+
+const AlertTitle = React.forwardRef<HTMLParagraphElement, React.HTMLAttributes<HTMLHeadingElement>>(
+  ({ className, ...props }, ref) => (
+    <h5
+      ref={ref}
+      className={cn('mb-1 leading-none font-medium tracking-tight', className)}
+      {...props}
+    />
+  ),
+);
+AlertTitle.displayName = 'AlertTitle';
+
+const AlertDescription = React.forwardRef<
+  HTMLParagraphElement,
+  React.HTMLAttributes<HTMLParagraphElement>
+>(({ className, ...props }, ref) => (
+  <div ref={ref} className={cn('text-sm [&_p]:leading-relaxed', className)} {...props} />
+));
+AlertDescription.displayName = 'AlertDescription';
+
+export { Alert, AlertTitle, AlertDescription };