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.

templates/tasks/main_view.php

@@ -3,6 +3,7 @@
     <i class="fa fa-plus"></i>Dodaj zadanie
   </a>
 </div>
+<div id="chart" style="margin-bottom: 25px;"></div>
 <div class="projects_container">
   <div class="left">
     <div class="_projects">
@@ -156,6 +157,25 @@
 
 </div>
 <script type="text/javascript">
+  <? if ( $this -> user['email'] == 'biuro@project-pro.pl' ):?>
+    $("#chart").gantt({
+    source: "/tasks/gantt_json/",
+    scale: "hours",
+    minScale: "hours",
+    maxScale: "months",
+    scaleStep: 1,
+    scrollToToday: false,
+    onItemClick: function(data) {
+        alert("Item clicked - show some details");
+    },
+    onAddClick: function(dt, rowId) {
+        alert("Empty space clicked - add an item!");
+    },
+    onRender: function() {
+        console.log("chart rendered");
+    }
+  });
+  <? endif;?>
   function reload_tasks( projects, users )
   {
     //load tasks by ajax

templates/tasks/task_edit.php

@@ -163,6 +163,15 @@ if ( is_array( $this -> clients ) )
     'type'    => 'checkbox'
 ] );
 ?>
+<?=
+\Html::input_switch( [
+    'label' => 'Pokaż w kalendarzu',
+    'name' => 'show_in_calendar',
+    'id' => 'show_in_calendar',
+    'checked' => $this -> task[ 'show_in_calendar' ] ? true : false,
+    'type' => 'checkbox'
+] );
+?>
 <? if ( $this -> task['id'] ):?>
   <div class="form-group row">
     <label class="col-md-3 col-form-label"></label>