feat(ui): add month view with income entry and post table

Negative remaining balances are shown in a warning treatment; nothing
blocks going over budget.

Applies the Tasks 18-23 design contract: --paper/--ink/--rule/--accent/
--surplus/--overspend tokens and the three type-role font variables in
src/index.css, --font-money on every money figure, and the carry meter
(a 3px hard-stopped gradient beneath each PostTable row) encoding
carried-in surplus, allocation track, spend fill and overrun.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/components/ui/button.tsx

@@ -1,28 +1,32 @@
-import { Slot } from "@radix-ui/react-slot";
-import { cva, type VariantProps } from "class-variance-authority";
-import * as React from "react";
+import * as React from "react"
+import { cva, type VariantProps } from "class-variance-authority"
+import { Slot } from "radix-ui"
 
-import { cn } from "@/lib/utils";
+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",
+  "inline-flex shrink-0 items-center justify-center gap-2 rounded-md text-sm font-medium whitespace-nowrap transition-all outline-none focus-visible:border-ring focus-visible:ring-[3px] focus-visible:ring-ring/50 disabled:pointer-events-none disabled:opacity-50 aria-invalid:border-destructive aria-invalid:ring-destructive/20 dark:aria-invalid:ring-destructive/40 [&_svg]:pointer-events-none [&_svg]:shrink-0 [&_svg:not([class*='size-'])]:size-4",
   {
     variants: {
       variant: {
         default: "bg-primary text-primary-foreground hover:bg-primary/90",
         destructive:
-          "bg-destructive text-white hover:bg-destructive/90 focus-visible:ring-destructive/20 dark:focus-visible:ring-destructive/40 dark:bg-destructive/60",
+          "bg-destructive text-white hover:bg-destructive/90 focus-visible:ring-destructive/20 dark:bg-destructive/60 dark:focus-visible:ring-destructive/40",
         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 hover:bg-secondary/80",
-        ghost: "hover:bg-accent hover:text-accent-foreground dark:hover:bg-accent/50",
+          "border bg-background shadow-xs hover:bg-accent hover:text-accent-foreground dark:border-input dark:bg-input/30 dark:hover:bg-input/50",
+        secondary:
+          "bg-secondary text-secondary-foreground 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",
+        xs: "h-6 gap-1 rounded-md px-2 text-xs has-[>svg]:px-1.5 [&_svg:not([class*='size-'])]:size-3",
+        sm: "h-8 gap-1.5 rounded-md px-3 has-[>svg]:px-2.5",
         lg: "h-10 rounded-md px-6 has-[>svg]:px-4",
         icon: "size-9",
+        "icon-xs": "size-6 rounded-md [&_svg:not([class*='size-'])]:size-3",
         "icon-sm": "size-8",
         "icon-lg": "size-10",
       },
@@ -31,22 +35,30 @@ const buttonVariants = cva(
       variant: "default",
       size: "default",
     },
-  },
-);
+  }
+)
 
 function Button({
   className,
-  variant,
-  size,
+  variant = "default",
+  size = "default",
   asChild = false,
   ...props
 }: React.ComponentProps<"button"> &
   VariantProps<typeof buttonVariants> & {
-    asChild?: boolean;
+    asChild?: boolean
   }) {
-  const Comp = asChild ? Slot : "button";
+  const Comp = asChild ? Slot.Root : "button"
 
-  return <Comp data-slot="button" className={cn(buttonVariants({ variant, size, className }))} {...props} />;
+  return (
+    <Comp
+      data-slot="button"
+      data-variant={variant}
+      data-size={size}
+      className={cn(buttonVariants({ variant, size, className }))}
+      {...props}
+    />
+  )
 }
 
-export { Button, buttonVariants };
+export { Button, buttonVariants }