fix(ui): refine amount entry, date warnings and booking actions

tests/Duempelkas.Tests/BookingDateInputTests.cs

@@ -0,0 +1,26 @@
+using Bunit;
+using Duempelkas.App.Components;
+using Xunit;
+
+namespace Duempelkas.Tests;
+
+public class BookingDateInputTests
+{
+    [Fact]
+    public void DateIsValidatedOnLeavingField_WithoutInterruptingNativeCalendar()
+    {
+        using var context = new BunitContext();
+        var value = "2025-12-31";
+        var field = context.Render<BookingDateInput>(p => p
+            .Add(x => x.Value, value).Add(x => x.ValueChanged, next => value = next));
+        field.Find("input").Input("2026-01-01");
+        Assert.Equal("2025-12-31", value);
+        field.Find("input").Blur();
+        Assert.Equal("2026-01-01", value);
+        field.Render(p => p.Add(x => x.Value, value));
+        // The browser owns the edited value; avoid resetting its calendar by writing it back.
+        Assert.Equal("2025-12-31", field.Find("input").GetAttribute("value"));
+        field.Render(p => p.Add(x => x.Value, "2027-02-03"));
+        Assert.Equal("2027-02-03", field.Find("input").GetAttribute("value"));
+    }
+}