Smart opened-product expiry: days countdown, edibility, correct sort

PHP getStats() opened section:
- Primary detection: opened_at IS NOT NULL (reliable, set by useFromInventory)
  Fallback: fractional-qty pattern (legacy items)
- Per-item compute opened_expiry = min(opened_at + estimateOpenedExpiryDaysPHP, original_expiry)
  → vacuum_sealed items get 1.5× multiplier
  → always take sooner of 'opened shelf life' vs 'original sealed expiry'
- Add days_to_expiry, opened_expiry, is_edible, has_opened_at to each item
- Filter legacy items (no opened_at) with expiry > 14 days (too much noise)
- Sort by days_to_expiry ASC (soonest/spoiled first) instead of updated_at DESC

JS dashboard opened render:
- Expiry badge: ⛔ Scaduto / ⚠️ Scade oggi / ⏰ Xgg (urgent≤2, soon≤5, ok>5)
- 🔒 icon added when vacuum_sealed=1
- Spoiled items shown with strikethrough name + muted styling (.alert-item-spoiled)
- Cap display at 10 items; 'e altri N prodotti aperti...' note if more
- Sort comes from server (removed JS openedFraction sort)

CSS:
- .opened-expiry-{ok,soon,urgent,today,spoiled} badge classes
- .alert-item-spoiled strikethrough styling
- .alert-more-note

assets/css/style.css

@@ -4304,6 +4304,34 @@ body {
     font-size: 0.7rem;
 }
 
+/* Opened expiry badges */
+.alert-item-badge.opened-expiry {
+    font-size: 0.7rem;
+    font-weight: 700;
+    border-radius: 20px;
+    padding: 2px 7px;
+}
+.opened-expiry-ok      { background: #dcfce7; color: #166534; }
+.opened-expiry-soon    { background: #fef9c3; color: #854d0e; }
+.opened-expiry-urgent  { background: #fee2e2; color: #991b1b; }
+.opened-expiry-today   { background: #f97316; color: #fff; }
+.opened-expiry-spoiled { background: #1f2937; color: #f9fafb; }
+
+.alert-item-spoiled {
+    opacity: 0.75;
+}
+.alert-item-spoiled .alert-item-name {
+    text-decoration: line-through;
+    color: var(--text-light);
+}
+
+.alert-more-note {
+    font-size: 0.8rem;
+    color: var(--text-light);
+    text-align: center;
+    padding: 6px 0 2px;
+}
+
 .review-hint {
     font-size: 0.8rem;
     color: #92400e;