feat: full shadcn/ui component system with consistent typography

New components:
- ui/button.tsx — Button with primary/accent/surface/ghost/destructive variants
- ui/input.tsx — Input + Textarea with focus ring and CSS var theming
- ui/label.tsx — Radix Label with peer-disabled support
- ui/separator.tsx — Radix Separator
- ui/tooltip.tsx — Radix Tooltip with themed content
- ui/dialog.tsx — Radix Dialog replacing custom modal implementations
- ui/table.tsx — Table/TableHeader/TableBody/TableRow/TableHead/TableCell
- ui/typography.tsx — PageTitle/SectionHeading/Body/Muted/Caption/MonoCaption

Wired throughout all components:
- ConfirmDialog + FormModal migrated to Radix Dialog (focus trap, Escape, ARIA)
- All raw <button> → Button, <input>/<textarea> → Input/Textarea
- All repeated text patterns → typography components
- All hardcoded hex/rgba strings → COLOR constants

src/components/ui/button.tsx

@@ -0,0 +1,70 @@
+import { cn } from "@/lib/utils";
+import { Slot } from "@radix-ui/react-slot";
+import { type VariantProps, cva } from "class-variance-authority";
+import { forwardRef } from "react";
+
+const buttonVariants = cva(
+	[
+		"inline-flex items-center justify-center gap-1.5 rounded-lg font-medium transition-all",
+		"focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-offset-2 focus-visible:ring-offset-[var(--bg-1)]",
+		"disabled:opacity-50 disabled:pointer-events-none",
+	],
+	{
+		variants: {
+			variant: {
+				primary: [
+					"text-white",
+					"[background:var(--accent)]",
+					"focus-visible:ring-[var(--accent)]",
+				],
+				accent: [
+					"[background:var(--accent-dim)] [color:var(--accent-text)]",
+					"[border:1px_solid_var(--accent-border)]",
+					"focus-visible:ring-[var(--accent)]",
+				],
+				surface: [
+					"[background:var(--surface)] [color:var(--text-2)]",
+					"[border:1px_solid_var(--border)]",
+					"focus-visible:ring-[var(--border)]",
+				],
+				ghost: [
+					"[color:var(--text-3)]",
+					"hover:[background:var(--surface)]",
+					"focus-visible:ring-[var(--border)]",
+				],
+				destructive: [
+					"bg-[rgba(239,68,68,0.08)] text-[#f87171]",
+					"border border-[rgba(239,68,68,0.2)]",
+					"focus-visible:ring-[#f87171]",
+				],
+			},
+			size: {
+				default: "px-4 py-2 text-sm",
+				sm: "px-3 py-1.5 text-xs",
+				icon: "p-1.5 text-sm",
+			},
+		},
+		defaultVariants: {
+			variant: "accent",
+			size: "default",
+		},
+	},
+);
+
+export interface ButtonProps
+	extends React.ButtonHTMLAttributes<HTMLButtonElement>,
+		VariantProps<typeof buttonVariants> {
+	asChild?: boolean;
+}
+
+export const Button = forwardRef<HTMLButtonElement, ButtonProps>(
+	({ className, variant, size, asChild = false, ...props }, ref) => {
+		const Comp = asChild ? Slot : "button";
+		return (
+			<Comp ref={ref} className={cn(buttonVariants({ variant, size }), className)} {...props} />
+		);
+	},
+);
+Button.displayName = "Button";
+
+export { buttonVariants };