feat: Integrate JS Gantt Chart library and update styles

- Added JS Gantt Chart library files including CSS and JS.
- Updated existing Gantt chart styles for better visual representation.
- Translated month and day names to Polish in the Gantt chart settings.
- Implemented Gantt chart initialization in the main view with sample data.
- Added a toggle switch for displaying tasks in the calendar.
- Enhanced task edit form with a new checkbox for calendar visibility.
- Improved the layout of the logged-in user template to include Gantt chart styles and scripts.

autoload/factory/class.Tasks.php

@@ -311,7 +311,7 @@ class Tasks
   }
 
   // przy zmianach pamiętać o zadaniach z CRON
-  static public function task_save( $task_id, $parent_id = null, $user_id, $name, $text, $date_start, $date_end, $project_id, $client_id, $pay_rate, $reminders_interval, $recursively, $frequency, $period, $users, $date_end_month_day = null, $date_start_month_day = null, $send_email_notification = false, $status_change_mail, $rescursive = false, $status = 0 )
+  static public function task_save( $task_id, $parent_id = null, $user_id, $name, $text, $date_start, $date_end, $project_id, $client_id, $pay_rate, $reminders_interval, $recursively, $frequency, $period, $users, $date_end_month_day = null, $date_start_month_day = null, $send_email_notification = false, $status_change_mail, $rescursive = false, $status = 0, $show_in_calendar )
   {
     global $mdb;
 
@@ -337,7 +337,8 @@ class Tasks
         'date_start_month_day' => $date_start_month_day,
         'status_change_mail' => $status_change_mail == 'on' ? 1 : 0,
         'o' => ++$order,
-        'status' => $status
+        'status' => $status,
+        'show_in_calendar' => $show_in_calendar == 'on' ? 1 : 0,
       ] );
       $id = $mdb -> id();
 
@@ -377,7 +378,8 @@ class Tasks
         'period' => $period,
         'reminders_send' => 0,
         'status_change_mail' => $status_change_mail == 'on' ? 1 : 0,
-        'status' => $status
+        'status' => $status,
+        'show_in_calendar' => $show_in_calendar == 'on' ? 1 : 0,
       ], [
         'AND' => [
           'id' => $task_id