Fix models database calls and structural updates

backend/app/Models/Campaign.php

@@ -13,15 +13,15 @@ class Campaign extends BaseModel
     /**
      * Get all campaigns for a company
      */
-    public function findAllByCompany(int $companyId)
+    public static function findAllByCompany(int $companyId)
     {
-        return $this->db->query(
+        return \App\Core\Database::select(
             "SELECT c.*, g.name as group_name, t.name as template_name 
-             FROM {$this->table} c
+             FROM " . static::$table . " c
              LEFT JOIN contact_groups g ON c.group_id = g.id
              LEFT JOIN templates t ON c.template_id = t.id
              WHERE c.company_id = ? ORDER BY c.id DESC",
             [$companyId]
-        )->fetchAll();
+        );
     }
 }