feat: add Client billing fields to store, /clients route, and reorder NavRail

src/components/NavRail.vue

@@ -5,6 +5,7 @@ import { useTimerStore } from '../stores/timer'
 import {
   LayoutDashboard,
   Clock,
+  Users,
   FolderKanban,
   List,
   BarChart3,
@@ -19,10 +20,11 @@ const timerStore = useTimerStore()
 const navItems = [
   { name: 'Dashboard', path: '/', icon: LayoutDashboard },
   { name: 'Timer', path: '/timer', icon: Clock },
+  { name: 'Clients', path: '/clients', icon: Users },
   { name: 'Projects', path: '/projects', icon: FolderKanban },
   { name: 'Entries', path: '/entries', icon: List },
-  { name: 'Reports', path: '/reports', icon: BarChart3 },
   { name: 'Invoices', path: '/invoices', icon: FileText },
+  { name: 'Reports', path: '/reports', icon: BarChart3 },
   { name: 'Settings', path: '/settings', icon: Settings }
 ]