fix: guard BottomSheet document access for SSR compatibility

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

opal-web/src/lib/components/BottomSheet.svelte

@@ -1,5 +1,6 @@
 <script>
 	import { onMount, onDestroy } from 'svelte';
+	import { browser } from '$app/environment';
 
 	/** @type {boolean} */
 	export let open = false;
@@ -29,13 +30,15 @@
 	let sheetEl = null;
 
 	// Body scroll lock
-	$: if (open) {
-		document.documentElement.style.overflow = 'hidden';
-	} else {
-		document.documentElement.style.overflow = '';
-		dragOffset = 0;
-		dragging = false;
-		locked = false;
+	$: if (browser) {
+		if (open) {
+			document.documentElement.style.overflow = 'hidden';
+		} else {
+			document.documentElement.style.overflow = '';
+			dragOffset = 0;
+			dragging = false;
+			locked = false;
+		}
 	}
 
 	/**