feat: Fix loan API type assertion and complete core loan features

- Resolve interface conversion panic in loan handlers by correcting
  user type assertions from *models.User to models.User
- Finalize loan management API integration with frontend components
- Implement remaining loan calculation logic and CRUD operations
- Connect loan display components to backend APIs as per Phase 3
- Update project status in README.md to reflect completed loan features
- Add CORS middleware configuration for frontend-backend communication

This commit completes core loan management functionality and fixes critical
type safety issues in the API handlers, enabling proper user context handling.

1 files changed, 59 insertions, 0 deletions

diff --git a/frontend/src/components/ui/button.tsx b/frontend/src/components/ui/button.tsx
new file mode 100644
index 0000000..a2df8dc
--- /dev/null
+++ b/frontend/src/components/ui/button.tsx
@@ -0,0 +1,59 @@
+import * as React from "react"
+import { Slot } from "@radix-ui/react-slot"
+import { cva, type VariantProps } from "class-variance-authority"
+
+import { cn } from "@/lib/utils"
+
+const buttonVariants = cva(
+  "inline-flex items-center justify-center gap-2 whitespace-nowrap rounded-md text-sm font-medium transition-all disabled:pointer-events-none disabled:opacity-50 [&_svg]:pointer-events-none [&_svg:not([class*='size-'])]:size-4 shrink-0 [&_svg]:shrink-0 outline-none focus-visible:border-ring focus-visible:ring-ring/50 focus-visible:ring-[3px] aria-invalid:ring-destructive/20 dark:aria-invalid:ring-destructive/40 aria-invalid:border-destructive",
+  {
+    variants: {
+      variant: {
+        default:
+          "bg-primary text-primary-foreground shadow-xs hover:bg-primary/90",
+        destructive:
+          "bg-destructive text-white shadow-xs hover:bg-destructive/90 focus-visible:ring-destructive/20 dark:focus-visible:ring-destructive/40 dark:bg-destructive/60",
+        outline:
+          "border bg-background shadow-xs hover:bg-accent hover:text-accent-foreground dark:bg-input/30 dark:border-input dark:hover:bg-input/50",
+        secondary:
+          "bg-secondary text-secondary-foreground shadow-xs hover:bg-secondary/80",
+        ghost:
+          "hover:bg-accent hover:text-accent-foreground dark:hover:bg-accent/50",
+        link: "text-primary underline-offset-4 hover:underline",
+      },
+      size: {
+        default: "h-9 px-4 py-2 has-[>svg]:px-3",
+        sm: "h-8 rounded-md gap-1.5 px-3 has-[>svg]:px-2.5",
+        lg: "h-10 rounded-md px-6 has-[>svg]:px-4",
+        icon: "size-9",
+      },
+    },
+    defaultVariants: {
+      variant: "default",
+      size: "default",
+    },
+  }
+)
+
+function Button({
+  className,
+  variant,
+  size,
+  asChild = false,
+  ...props
+}: React.ComponentProps<"button"> &
+  VariantProps<typeof buttonVariants> & {
+    asChild?: boolean
+  }) {
+  const Comp = asChild ? Slot : "button"
+
+  return (
+    <Comp
+      data-slot="button"
+      className={cn(buttonVariants({ variant, size, className }))}
+      {...props}
+    />
+  )
+}
+
+export { Button, buttonVariants }