fix(frontend): show version numbers oldest-first (1 = oldest)

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

frontend/src/routes/documents/[id]/+page.svelte

@@ -307,7 +307,7 @@ function formatDateTime(iso: string): string {
 }
 
 function versionLabel(v: VersionSummary, index: number): string {
-	return `Version ${versions.length - index} — ${v.editorName} — ${formatDateTime(v.savedAt)}`;
+	return `Version ${index + 1} — ${v.editorName} — ${formatDateTime(v.savedAt)}`;
 }
 </script>
 
@@ -720,7 +720,7 @@ function versionLabel(v: VersionSummary, index: number): string {
 												>
 													<div class="flex items-baseline justify-between gap-2">
 														<span class="font-sans text-xs font-medium text-brand-navy">
-															Version {versions.length - i}
+															Version {i + 1}
 														</span>
 														<span class="font-sans text-[10px] text-gray-400">
 															{formatDateTime(v.savedAt)}