feat(ui): company list page with columns, filters, and sidebar entry

src/components/layout/sidebar.tsx

@@ -9,6 +9,7 @@ import {
   Bookmark,
   Anchor,
   Ship,
+  Building2,
   Receipt,
   FileText,
   FolderOpen,
@@ -62,6 +63,7 @@ function buildNavSections(portSlug: string | undefined): NavSection[] {
         { href: `${base}/dashboard`, label: 'Dashboard', icon: LayoutDashboard },
         { href: `${base}/clients`, label: 'Clients', icon: Users },
         { href: `${base}/yachts`, label: 'Yachts', icon: Ship },
+        { href: `${base}/companies`, label: 'Companies', icon: Building2 },
         { href: `${base}/interests`, label: 'Interests', icon: Bookmark },
         { href: `${base}/berths`, label: 'Berths', icon: Anchor },
       ],