feat: anomaly detection banner - notifica incongruenze inventario/transazioni

- New API endpoint 'inventory_anomalies': detects items where stored qty
  differs from tx history by >20% AND >50 units (phantom qty or missing qty)
- New API endpoint 'dismiss_anomaly': persists dismissal in anomaly_dismissed.json
- Banner system: new 'anomaly' type shown in dashboard alert banner
  with 'Correggi' (opens edit) and 'Ok, ignora' (dismisses) buttons
- CSS: banner-anomaly style (orange gradient)
- Fix: lo zucchero azzerato (175g fantasma rimossi), aggiunto a Bring!

index.html

@@ -11,7 +11,7 @@
     <title>EverShelf</title>
     <link rel="manifest" href="manifest.json">
     <link rel="icon" type="image/svg+xml" href="data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 100 100'><text y='.9em' font-size='90'>🏠</text></svg>">
-    <link rel="stylesheet" href="assets/css/style.css?v=20260420a">
+    <link rel="stylesheet" href="assets/css/style.css?v=20260421a">
     <!-- QuaggaJS for barcode scanning -->
     <script src="https://cdn.jsdelivr.net/npm/@ericblade/quagga2@1.8.4/dist/quagga.min.js"></script>
 </head>
@@ -1288,6 +1288,6 @@
     </div>
 </div>
 
-<script src="assets/js/app.js?v=20260420a"></script>
+<script src="assets/js/app.js?v=20260421a"></script>
 </body>
 </html>