feat: wrap App with ToastProvider for global notifications

client/src/App.jsx

@@ -2,6 +2,7 @@ import React, { useState } from 'react';
 import ViolationForm from './components/ViolationForm';
 import Dashboard     from './components/Dashboard';
 import ReadmeModal   from './components/ReadmeModal';
+import ToastProvider from './components/ToastProvider';
 
 const tabs = [
   { id: 'dashboard', label: '📊 Dashboard' },
@@ -45,6 +46,7 @@ export default function App() {
   const [showReadme, setShowReadme] = useState(false);
 
   return (
+    <ToastProvider>
       <div style={s.app}>
         <nav style={s.nav}>
           <div style={s.logoWrap}>
@@ -69,5 +71,6 @@ export default function App() {
 
         {showReadme && <ReadmeModal onClose={() => setShowReadme(false)} />}
       </div>
+    </ToastProvider>
   );
 }