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/tabs.tsx

@@ -1,52 +1,56 @@
-import * as React from 'react';
-import * as TabsPrimitive from '@radix-ui/react-tabs';
-import { cn } from '@/lib/utils';
-
-const Tabs = TabsPrimitive.Root;
-
-const TabsList = React.forwardRef<
-  React.ElementRef<typeof TabsPrimitive.List>,
-  React.ComponentPropsWithoutRef<typeof TabsPrimitive.List>
->(({ className, ...props }, ref) => (
-  <TabsPrimitive.List
-    ref={ref}
-    className={cn(
-      'bg-muted/30 text-muted-foreground inline-flex h-10 items-center justify-center rounded-md p-1 border border-white/5',
-      className,
-    )}
-    {...props}
-  />
-));
-TabsList.displayName = TabsPrimitive.List.displayName;
-
-const TabsTrigger = React.forwardRef<
-  React.ElementRef<typeof TabsPrimitive.Trigger>,
-  React.ComponentPropsWithoutRef<typeof TabsPrimitive.Trigger>
->(({ className, ...props }, ref) => (
-  <TabsPrimitive.Trigger
-    ref={ref}
-    className={cn(
-      'ring-offset-background focus-visible:ring-ring data-[state=active]:bg-background data-[state=active]:text-foreground inline-flex items-center justify-center rounded-sm px-3 py-1.5 text-sm font-medium whitespace-nowrap transition-all focus-visible:ring-2 focus-visible:ring-offset-2 focus-visible:outline-none disabled:pointer-events-none disabled:opacity-50 data-[state=active]:shadow-none data-[state=active]:border data-[state=active]:border-white/10',
-      className,
-    )}
-    {...props}
-  />
-));
-TabsTrigger.displayName = TabsPrimitive.Trigger.displayName;
-
-const TabsContent = React.forwardRef<
-  React.ElementRef<typeof TabsPrimitive.Content>,
-  React.ComponentPropsWithoutRef<typeof TabsPrimitive.Content>
->(({ className, ...props }, ref) => (
-  <TabsPrimitive.Content
-    ref={ref}
-    className={cn(
-      'ring-offset-background focus-visible:ring-ring mt-2 focus-visible:ring-2 focus-visible:ring-offset-2 focus-visible:outline-none',
-      className,
-    )}
-    {...props}
-  />
-));
-TabsContent.displayName = TabsPrimitive.Content.displayName;
-
-export { Tabs, TabsList, TabsTrigger, TabsContent };
+import * as React from 'react';
+import * as TabsPrimitive from '@radix-ui/react-tabs';
+import { cn } from '@/lib/utils';
+
+const Tabs = TabsPrimitive.Root;
+
+const TabsList = React.forwardRef<
+  React.ElementRef<typeof TabsPrimitive.List>,
+  React.ComponentPropsWithoutRef<typeof TabsPrimitive.List>
+>(({ className, ...props }, ref) => (
+  <TabsPrimitive.List
+    ref={ref}
+    className={cn(
+      'bg-muted/40 text-muted-foreground inline-flex h-9 items-center justify-center rounded-lg p-1 border border-white/[0.04]',
+      className,
+    )}
+    {...props}
+  />
+));
+TabsList.displayName = TabsPrimitive.List.displayName;
+
+const TabsTrigger = React.forwardRef<
+  React.ElementRef<typeof TabsPrimitive.Trigger>,
+  React.ComponentPropsWithoutRef<typeof TabsPrimitive.Trigger>
+>(({ className, ...props }, ref) => (
+  <TabsPrimitive.Trigger
+    ref={ref}
+    className={cn(
+      'inline-flex items-center justify-center rounded-md px-3 py-1 text-[13px] font-medium whitespace-nowrap transition-all duration-200',
+      'text-muted-foreground hover:text-foreground',
+      'data-[state=active]:bg-background data-[state=active]:text-foreground data-[state=active]:shadow-sm data-[state=active]:border data-[state=active]:border-white/[0.08]',
+      'focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring/30',
+      'disabled:pointer-events-none disabled:opacity-50',
+      className,
+    )}
+    {...props}
+  />
+));
+TabsTrigger.displayName = TabsPrimitive.Trigger.displayName;
+
+const TabsContent = React.forwardRef<
+  React.ElementRef<typeof TabsPrimitive.Content>,
+  React.ComponentPropsWithoutRef<typeof TabsPrimitive.Content>
+>(({ className, ...props }, ref) => (
+  <TabsPrimitive.Content
+    ref={ref}
+    className={cn(
+      'mt-3 animate-in focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring/30',
+      className,
+    )}
+    {...props}
+  />
+));
+TabsContent.displayName = TabsPrimitive.Content.displayName;
+
+export { Tabs, TabsList, TabsTrigger, TabsContent };