feat: add dashboard widget with placeholder template

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

EventSubscriber/DashboardSubscriber.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace KimaiPlugin\KimaiHeatmapBundle\EventSubscriber;
+
+use App\Event\DashboardEvent;
+use App\Widget\WidgetService;
+use Symfony\Component\EventDispatcher\EventSubscriberInterface;
+
+final class DashboardSubscriber implements EventSubscriberInterface
+{
+    public function __construct(private readonly WidgetService $widgetService)
+    {
+    }
+
+    public static function getSubscribedEvents(): array
+    {
+        return [
+            DashboardEvent::class => ['onDashboard', 100],
+        ];
+    }
+
+    public function onDashboard(DashboardEvent $event): void
+    {
+        $widget = $this->widgetService->getWidget('HeatmapWidget');
+        if ($widget !== null) {
+            $event->addWidget($widget);
+        }
+    }
+}

Resources/views/widget/heatmap.html.twig

@@ -0,0 +1,10 @@
+{% embed '@theme/embeds/card.html.twig' with {'margin_bottom': 0} %}
+    {% block box_title %}
+        {{ title }}
+    {% endblock %}
+    {% block box_body %}
+        <div id="heatmap-container" data-url="{{ path('heatmap_data') }}" style="min-height: 150px; padding: 1rem;">
+            <p style="color: var(--bs-secondary);">Heatmap visualization coming in Phase 3</p>
+        </div>
+    {% endblock %}
+{% endembed %}

Widget/HeatmapWidget.php

@@ -0,0 +1,44 @@
+<?php
+
+namespace KimaiPlugin\KimaiHeatmapBundle\Widget;
+
+use App\Widget\Type\AbstractWidget;
+use App\Widget\WidgetInterface;
+
+final class HeatmapWidget extends AbstractWidget
+{
+    public function getId(): string
+    {
+        return 'HeatmapWidget';
+    }
+
+    public function getTitle(): string
+    {
+        return 'Activity Heatmap';
+    }
+
+    public function getWidth(): int
+    {
+        return WidgetInterface::WIDTH_FULL;
+    }
+
+    public function getHeight(): int
+    {
+        return WidgetInterface::HEIGHT_LARGE;
+    }
+
+    public function getPermissions(): array
+    {
+        return ['view_own_timesheet'];
+    }
+
+    public function getData(array $options = []): mixed
+    {
+        return null;
+    }
+
+    public function getTemplateName(): string
+    {
+        return '@KimaiHeatmapBundle/widget/heatmap.html.twig';
+    }
+}