Fix Collection unique() to handle numeric strings correctly

Fixes bug where SORT_REGULAR incorrectly deduplicates numeric strings
when a '+' prefix is present. Collections like ['+19495551234',
'9495551234', '19495551234'] now correctly return all three items
instead of incorrectly removing the 11-digit format.

The fix checks if the collection contains complex types (arrays/objects)
that require SORT_REGULAR, or scalar values where default array_unique()
is faster and more correct.

This works around a documented PHP limitation with SORT_REGULAR where
numeric strings are compared as numbers in certain contexts, causing
unexpected deduplication behavior.

See: php/doc-en#1463
Related to: 48a53be

Author: jmarble

src/Illuminate/Collections/Collection.php

@@ -1771,8 +1771,14 @@ public function undot()
      */
     public function unique($key = null, $strict = false)
     {
-        if (is_null($key) && $strict === false) {
-            return new static(array_unique($this->items, SORT_REGULAR));
+        if ($key === null && $strict === false) {
+            foreach ($this->items as $item) {
+                if (! is_scalar($item) && $item !== null) {
+                    return new static(array_unique($this->items, SORT_REGULAR));
+                }
+            }
+
+            return new static(array_unique($this->items));
         }
 
         $callback = $this->valueRetriever($key);