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/input.tsx

@@ -1,23 +1,26 @@
-import * as React from 'react';
-import { cn } from '@/lib/utils';
-
-export interface InputProps extends React.InputHTMLAttributes<HTMLInputElement> {}
-
-const Input = React.forwardRef<HTMLInputElement, InputProps>(
-  ({ className, type, ...props }, ref) => {
-    return (
-      <input
-        type={type}
-        className={cn(
-          'border-input placeholder:text-muted-foreground focus-visible:ring-ring focus-visible:border-primary flex h-10 w-full rounded-md border bg-background px-3 py-2 text-sm transition-colors file:border-0 file:bg-transparent file:text-sm file:font-medium focus-visible:outline-none disabled:cursor-not-allowed disabled:opacity-50',
-          className,
-        )}
-        ref={ref}
-        {...props}
-      />
-    );
-  },
-);
-Input.displayName = 'Input';
-
-export { Input };
+import * as React from 'react';
+
+import { cn } from '@/lib/utils';
+
+const Input = React.forwardRef<HTMLInputElement, React.ComponentProps<'input'>>(
+  ({ className, type, ...props }, ref) => {
+    return (
+      <input
+        type={type}
+        className={cn(
+          'flex h-9 w-full rounded-lg border border-white/[0.08] bg-muted/50 px-3 py-1 text-[13px] text-foreground shadow-none transition-colors duration-200',
+          'file:border-0 file:bg-transparent file:text-sm file:font-medium file:text-foreground',
+          'placeholder:text-muted-foreground',
+          'focus-visible:outline-none focus-visible:border-accent/50 focus-visible:ring-1 focus-visible:ring-accent/20',
+          'disabled:cursor-not-allowed disabled:opacity-50',
+          className,
+        )}
+        ref={ref}
+        {...props}
+      />
+    );
+  },
+);
+Input.displayName = 'Input';
+
+export { Input };