Migrate icon buttons to Button component and simplify size variants

Replace raw <button> elements with Button variant="ghost" in stat-block
panel, toast, player modals. Add icon-sm size variant (h-6 w-6) for
compact contexts. Consolidate text button sizes into a single default
(h-8 px-3), removing the redundant sm variant. Add size prop to
ConfirmButton for consistent sizing.

Button now has three sizes: default (text), icon, icon-sm.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

apps/web/src/components/ui/button.tsx

@@ -13,9 +13,9 @@ const buttonVariants = cva(
 				ghost: "hover:bg-hover-neutral-bg hover:text-hover-neutral",
 			},
 			size: {
-				default: "h-9 px-4 py-2",
-				sm: "h-8 px-3 text-xs",
+				default: "h-8 px-3 text-xs",
 				icon: "h-8 w-8",
+				"icon-sm": "h-6 w-6",
 			},
 		},
 		defaultVariants: {