refactor: remove gh/GitHub references from tokens, classes, and component names

Rename all --color-gh-* CSS tokens to --color-*, update Tailwind class names
(bg-gh-*, text-gh-*, border-gh-*, etc.) across all TSX/TS files, rename
GhButton component and file to Button, and remove trivial descriptive comments.

src/components/ui/Button.tsx

@@ -1,46 +1,47 @@
-import { forwardRef, ButtonHTMLAttributes } from 'react';
 import { cn } from '@/lib/utils';
-import { LoadingSpinner } from './LoadingSpinner';
+import { ButtonHTMLAttributes } from 'react';
+
+type ButtonVariant = 'primary' | 'ghost' | 'danger-outline' | 'danger-solid';
+type ButtonSize = 'sm' | 'md';
 
 interface ButtonProps extends ButtonHTMLAttributes<HTMLButtonElement> {
-	variant?: 'primary' | 'secondary' | 'danger' | 'ghost';
-	size?: 'sm' | 'md' | 'lg';
-	isLoading?: boolean;
+	variant?: ButtonVariant;
+	size?: ButtonSize;
 }
 
-const baseClasses =
-	'inline-flex items-center justify-center font-medium rounded-md focus:outline-none focus:ring-2 focus:ring-offset-2 disabled:opacity-50 disabled:cursor-not-allowed';
-
-const variants = {
-	primary: 'bg-blue-600 text-white hover:bg-blue-700 focus:ring-blue-500',
-	secondary: 'bg-gray-600 text-white hover:bg-gray-700 focus:ring-gray-500',
-	danger: 'bg-red-600 text-white hover:bg-red-700 focus:ring-red-500',
-	ghost: 'text-gray-300 hover:text-white hover:bg-gray-700 focus:ring-gray-500'
+const variantClasses: Record<ButtonVariant, string> = {
+	primary: 'bg-btn-green border border-btn-green-hover text-white hover:bg-btn-green-hover',
+	ghost: 'bg-transparent border border-border text-secondary hover:bg-overlay hover:text-primary',
+	'danger-outline': 'bg-transparent border border-border text-red hover:border-red/40 hover:bg-red-bg',
+	'danger-solid': 'bg-overlay border border-red/20 text-red hover:bg-red-bg',
 };
 
-const sizes = {
-	sm: 'px-3 py-1 text-sm',
+const sizeClasses: Record<ButtonSize, string> = {
+	sm: 'px-3 py-1.5 text-xs',
 	md: 'px-4 py-2 text-sm',
-	lg: 'px-6 py-3 text-base'
 };
 
-export const Button = forwardRef<HTMLButtonElement, ButtonProps>(
-	(
-		{ className, variant = 'primary', size = 'md', isLoading, children, disabled, ...props },
-		ref
-	) => {
-		return (
-			<button
-				className={cn(baseClasses, variants[variant], sizes[size], className)}
-				disabled={disabled || isLoading}
-				ref={ref}
-				{...props}
-			>
-				{isLoading && <LoadingSpinner size="sm" className="mr-2" />}
-				{children}
-			</button>
-		);
-	}
-);
-
-Button.displayName = 'Button';
+export function Button({
+	variant = 'ghost',
+	size = 'md',
+	className,
+	children,
+	disabled,
+	...props
+}: ButtonProps) {
+	return (
+		<button
+			{...props}
+			disabled={disabled}
+			className={cn(
+				'inline-flex items-center gap-1.5 justify-center rounded-md font-medium transition-colors focus:outline-none focus:ring-2 focus:ring-blue focus:ring-offset-1 focus:ring-offset-base',
+				'disabled:cursor-not-allowed disabled:opacity-40',
+				variantClasses[variant],
+				sizeClasses[size],
+				className
+			)}
+		>
+			{children}
+		</button>
+	);
+}