fix: merge GridStackView into DashboardView (#19)

DashboardView and GridStackView rendered the same three charts from the
same hardcoded data, so every chart factory method existed twice. The
dashboard is now the GridStackLayout variant at @Route(""):

- GridStackView deleted, its grid/toolbar/chart factories moved into
  DashboardView, which keeps the point-click notifications the old
  dashboard had.
- Charts size to their widget (100%/100%) instead of a fixed 400px.
- MainLayout has one dashboard entry; nav.gridstack/page.gridstack keys
  dropped from all three bundles.
- Storage key is "dashboard" (was "gridstack-demo"), so a saved layout
  from the old route is not reused.
- GridStackViewTest renamed to DashboardViewTest, plus a test asserting
  the three charts render.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0124BiJikbhbiEsNfJxdWM69

src/test/java/com/example/views/DashboardViewTest.java

@@ -1,8 +1,11 @@
 package com.example.views;
 
 import com.example.Application;
+import com.example.components.BarChart;
 import com.example.components.GridStackItem;
 import com.example.components.GridStackLayout;
+import com.example.components.LineChart;
+import com.example.components.PieChart;
 import com.vaadin.browserless.SpringBrowserlessTest;
 import com.vaadin.browserless.ViewPackages;
 import com.vaadin.browserless.internal.ElementUtilsKt;
@@ -21,12 +24,12 @@ import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
 @SpringBootTest(classes = Application.class)
-@ViewPackages(classes = GridStackView.class)
-class GridStackViewTest extends SpringBrowserlessTest {
+@ViewPackages(classes = DashboardView.class)
+class DashboardViewTest extends SpringBrowserlessTest {
 
     @Test
     void view_rendersGridWithDefaultWidgets() {
-        navigate(GridStackView.class);
+        navigate(DashboardView.class);
 
         GridStackLayout grid = $view(GridStackLayout.class).first();
         assertNotNull(grid);
@@ -36,9 +39,18 @@ class GridStackViewTest extends SpringBrowserlessTest {
         assertTrue(layout.stream().allMatch(p -> p.w() > 0 && p.h() > 0));
     }
 
+    @Test
+    void view_rendersTheThreeCharts() {
+        navigate(DashboardView.class);
+
+        assertNotNull($view(LineChart.class).first());
+        assertNotNull($view(BarChart.class).first());
+        assertNotNull($view(PieChart.class).first());
+    }
+
     @Test
     void addAndCloseWidget_changesItemCount() {
-        navigate(GridStackView.class);
+        navigate(DashboardView.class);
 
         GridStackLayout grid = $view(GridStackLayout.class).first();
         int initial = grid.getLayout().size();
@@ -52,7 +64,7 @@ class GridStackViewTest extends SpringBrowserlessTest {
 
     @Test
     void closeButton_removesTheClickedWidgetOnly() {
-        navigate(GridStackView.class);
+        navigate(DashboardView.class);
 
         GridStackLayout grid = $view(GridStackLayout.class).first();
         GridStackItem first = $view(GridStackItem.class).first();
@@ -68,7 +80,7 @@ class GridStackViewTest extends SpringBrowserlessTest {
 
     @Test
     void closeListener_firesOnceItemIsDetached() {
-        navigate(GridStackView.class);
+        navigate(DashboardView.class);
 
         GridStackLayout grid = $view(GridStackLayout.class).first();
         GridStackItem item = $view(GridStackItem.class).first();
@@ -83,7 +95,7 @@ class GridStackViewTest extends SpringBrowserlessTest {
 
     @Test
     void nonClosableItem_hasNoCloseButton() {
-        navigate(GridStackView.class);
+        navigate(DashboardView.class);
 
         GridStackItem item = $view(GridStackItem.class).first();
         assertTrue(item.isClosable(), "items are closable by default");