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-fetch-prompt.tsx

@@ -88,11 +88,7 @@ export function SourceFetchPrompt({
 			</div>
 
 			<div className="flex items-center gap-2">
-				<Button
-					size="sm"
-					onClick={handleFetch}
-					disabled={status === "fetching" || !url}
-				>
+				<Button onClick={handleFetch} disabled={status === "fetching" || !url}>
 					{status === "fetching" ? (
 						<Loader2 className="mr-1 h-3 w-3 animate-spin" />
 					) : (
@@ -104,7 +100,6 @@ export function SourceFetchPrompt({
 				<span className="text-xs text-muted-foreground">or</span>
 
 				<Button
-					size="sm"
 					variant="outline"
 					onClick={() => fileInputRef.current?.click()}
 					disabled={status === "fetching"}