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/source-manager.tsx

@@ -48,7 +48,6 @@ export function SourceManager({ onCacheCleared }: SourceManagerProps) {
 					Cached Sources
 				</span>
 				<Button
-					size="sm"
 					variant="outline"
 					className="hover:text-hover-destructive hover:border-hover-destructive"
 					onClick={handleClearAll}