fix: token tracking pipeline + premium usage dashboard redesign

Backend fixes:
- Fix totalTokens defaulting to 0 when API omits totalTokenCount (now computes prompt+completion)
- Fix streaming metadata extraction: unwrap response wrapper in Anthropic/Gemini handlers
- Fix Zod schemas: handle SQL SUM(null) with nullable().transform()
- Add is_estimated column migration to token_usage table

Frontend redesign:
- Rewrite Usage page with area charts (nivo/line), horizontal bar model ranking
- StatCard: add trend indicators (% vs previous period) and inline SVG sparklines
- Premium color palette, prompt/completion ratio bar, top models mini-list
- Live indicator with 15s auto-refresh

Design system migration:
- Standardize all components on Gemini Nexus tokens (rounded-xl, border-white/[0.06])
- Refine UI components, proxy tabs, cloud account list, provider groups

src/components/ui/badge.tsx

@@ -1,31 +1,30 @@
-import * as React from 'react';
-import { cva, type VariantProps } from 'class-variance-authority';
-import { cn } from '@/lib/utils';
-
-const badgeVariants = cva(
-  'inline-flex items-center rounded-md border px-2.5 py-0.5 text-xs font-semibold transition-colors focus:outline-none focus:ring-2 focus:ring-ring focus:ring-offset-2',
-  {
-    variants: {
-      variant: {
-        default: 'border-transparent bg-primary text-primary-foreground shadow hover:bg-primary/80',
-        secondary:
-          'border-transparent bg-secondary text-secondary-foreground hover:bg-secondary/80',
-        destructive:
-          'border-transparent bg-destructive text-destructive-foreground shadow hover:bg-destructive/80',
-        outline: 'text-foreground',
-      },
-    },
-    defaultVariants: {
-      variant: 'default',
-    },
-  },
-);
-
-export interface BadgeProps
-  extends React.HTMLAttributes<HTMLDivElement>, VariantProps<typeof badgeVariants> {}
-
-function Badge({ className, variant, ...props }: BadgeProps) {
-  return <div className={cn(badgeVariants({ variant }), className)} {...props} />;
-}
-
-export { Badge, badgeVariants };
+import * as React from 'react';
+import { cn } from '@/lib/utils';
+import { cva, type VariantProps } from 'class-variance-authority';
+
+const badgeVariants = cva(
+  'inline-flex items-center rounded-md px-2 py-0.5 text-[11px] font-medium transition-colors focus:outline-none focus:ring-2 focus:ring-ring/30',
+  {
+    variants: {
+      variant: {
+        default: 'bg-accent/15 text-accent border border-accent/20',
+        secondary: 'bg-secondary text-secondary-foreground border border-white/[0.06]',
+        destructive: 'bg-destructive/15 text-red-400 border border-destructive/20',
+        outline: 'border border-white/[0.1] text-muted-foreground',
+      },
+    },
+    defaultVariants: {
+      variant: 'default',
+    },
+  },
+);
+
+function Badge({
+  className,
+  variant,
+  ...props
+}: React.HTMLAttributes<HTMLDivElement> & VariantProps<typeof badgeVariants>) {
+  return <div className={cn(badgeVariants({ variant }), className)} {...props} />;
+}
+
+export { Badge, badgeVariants };