press-releases: Publish-Rechte, Quota-Races & Slug vereinheitlichen

- Publish/Reject/Archive und changeStatus erzwingen konsistent
  press-releases:publish; changeStatus schloss die Lücke, über die das
  Status-Modal die Prüfung umging (Fix#1/H2).
- publish()/changeStatusFromAdmin sperren PM- und User-Zeile
  transaktional; QuotaExceededException wird in Admin-Publish und im
  Auto-Publish-Job abgefangen (Warnung statt 500 / bleibt in Review, Fix#3/M2).
- Slug-Erzeugung nur noch über HasUniqueSlug (generateUniqueSlug +
  saveWithUniqueSlugRetry), redundanter Controller-Helper entfernt (M3).
- API-/Legacy-Text wird vor der Persistenz sanitisiert (M6);
  Scheduler/Legacy-Tracking ignorieren soft-gelöschte PMs.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/Models/Concerns/HasUniqueSlug.php

@@ -4,6 +4,7 @@ namespace App\Models\Concerns;
 
 use Illuminate\Database\Eloquent\Builder;
 use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\QueryException;
 use Illuminate\Support\Str;
 
 /**
@@ -49,6 +50,37 @@ trait HasUniqueSlug
         return $slug;
     }
 
+    /**
+     * Persist the model and recover from a concurrent slug insert by
+     * regenerating the next available suffix.
+     *
+     * @param  array<string, mixed>  $scope
+     * @param  array<string, mixed>  $options
+     */
+    public function saveWithUniqueSlugRetry(
+        string $source,
+        array $scope = [],
+        array $options = [],
+        int $maxAttempts = 3,
+    ): bool {
+        for ($attempt = 1; $attempt <= $maxAttempts; $attempt++) {
+            try {
+                return $this->save($options);
+            } catch (QueryException $exception) {
+                if ($attempt === $maxAttempts || ! $this->isSlugUniqueConstraintViolation($exception)) {
+                    throw $exception;
+                }
+
+                $this->setAttribute(
+                    $this->slugColumn(),
+                    $this->generateUniqueSlug($source, $scope),
+                );
+            }
+        }
+
+        return false;
+    }
+
     /**
      * @param  array<string, mixed>  $scope
      */
@@ -98,6 +130,15 @@ trait HasUniqueSlug
         return 'item';
     }
 
+    private function isSlugUniqueConstraintViolation(QueryException $exception): bool
+    {
+        $message = Str::lower($exception->getMessage());
+        $isUniqueViolation = in_array((string) $exception->getCode(), ['23000', '23505'], true)
+            || Str::contains($message, ['unique constraint', 'duplicate entry', 'duplicate key']);
+
+        return $isUniqueViolation && Str::contains($message, $this->slugColumn());
+    }
+
     /**
      * Hook for models to add additional WHERE constraints (e.g. soft-deleted
      * records). Default: no additional constraints.