Fix transfer quantity, unify date format, align demo seeds

Stock Transfer list showed 0.00 (read in instead of out); stock-out/transfer forms show the location quantity; dates display as YYYY-MM-DD HH:mm:ss. Demo seeds map product accounts, use product names and supplier batches, and add demo_seed_assets.php.

demo_seed.php

@@ -532,9 +532,11 @@ foreach ($stockout_defs as $so) {
     $qty  = $so['qty'];
     $cost = $p['cost'];
     $uom  = $p['uom'];
+    // The batch is bought in from a supplier; only the stock-out goes to the customer.
+    $supplier_id = $supplier_ids[0];
 
     dbTransaction($pdo2, function ($pdo2) use (
-        $stockMgmt, $whMgmt, $company_id, $main_wh_id, $sku, $qty, $cost, $customer_id,
+        $stockMgmt, $whMgmt, $company_id, $main_wh_id, $sku, $qty, $cost, $customer_id, $supplier_id,
         $logging, $dispatch_in_marker, $dispatch_out_marker
     ) {
         $bin = findFreeBin($pdo2, $company_id, $main_wh_id);
@@ -549,7 +551,7 @@ foreach ($stockout_defs as $so) {
             'zone'        => $bin,
             'aisle'       => $bin,
             'bin'         => $bin,
-            'contact_id'  => $customer_id,
+            'contact_id'  => $supplier_id,
             'description' => $dispatch_in_marker,
         ], $logging, $in_uuid);
         $stockMgmt->approveStock($stock_id, $main_wh_id, 'in', $whMgmt);