Fix QA review findings: server-side validation, notes encoding, dashboard totals

Validate document lines on the server and recompute their totals, store notes with quotes/markup/emoji (utf8mb4, idempotent escaping, decode in form fields), exclude transfers from company-wide stock in/out, count revenue from confirmed orders only, one low-stock rule everywhere, list unapproved lots, natural bin sort, stable order/PO sort, status tiles that add up.

app/cron/alert_low_stock.php

@@ -1,28 +1,33 @@
 <?php
 /**
  * alert_low_stock.php — Called by Node.js scheduler daily at 8am.
- * Returns companies that have one or more SKUs below their min_stock threshold.
+ * Returns companies that have one or more low-stock products.
  * Response: { success: 1, alerts: [{ company_id, count }] }
  */
 require __DIR__ . '/../assets/utils/cron_auth.php';
 
+// Same rule as ReportManager::getLowStockItems(): counted per warehouse, at or
+// below the higher of reorder point and minimum stock.
 $sth = $pdo2->query(
     "SELECT e.company_id, COUNT(*) AS count
       FROM (
-          SELECT company_id, product_sku, SUM(total_in - total_out) AS balance
+          SELECT company_id, warehouse_id, product_sku, SUM(total_in - total_out) AS balance
           FROM etl_stock_summary
           WHERE company_id > 0
-          GROUP BY company_id, product_sku
+          GROUP BY company_id, warehouse_id, product_sku
       ) e
       JOIN md_product p
         ON p.sku        = e.product_sku
-      AND p.company_id = e.company_id
-      AND p.status     = 1
-      WHERE p.min_stock > 0
-        AND e.balance   < p.min_stock
+       AND p.company_id = e.company_id
+       AND p.status     > 0
+      JOIN md_warehouse w
+        ON w.id         = e.warehouse_id
+       AND w.company_id = e.company_id
+       AND w.status     = 1
+      WHERE GREATEST(p.reorder_point, p.min_stock) > 0
+        AND e.balance <= GREATEST(p.reorder_point, p.min_stock)
       GROUP BY e.company_id
       HAVING count > 0"
-
 );
 
 $answer['success'] = 1;