Theme: instant switching via ThemeChanged event

- Add static App.ThemeChanged event fired after resource dictionary swap
- Pages/controls subscribe OnAppearing and call reload on change
- Themes include Extreme/SecondaryTextColor tokens for dark and light

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

Xamarin.Neo4j/Xamarin.Neo4j/Xamarin.Neo4j/App.xaml.cs

@@ -1,4 +1,6 @@
+using System;
 using Microsoft.Maui.ApplicationModel;
+using Microsoft.Maui.Graphics;
 using Microsoft.Maui.Controls;
 using Microsoft.Maui.Controls.Xaml;
 using Xamarin.Neo4j.Pages;
@@ -10,15 +12,23 @@ namespace Xamarin.Neo4j
 {
     public partial class App : Application
     {
+        public static event EventHandler ThemeChanged;
+
         public App()
         {
             InitializeComponent();
 
             SetTheme(Current.RequestedTheme);
+            RequestedThemeChanged += (s, e) => SetTheme(e.RequestedTheme);
 
-            MainPage = new NavigationPage(new RootPage());
+            MainPage = new NavigationPage(new ConnectionsPage());
+
+            // SetTheme ran before MainPage was assigned, so apply bar colours now.
+            ApplyNavBarColors();
         }
 
+        public void UpdateTheme(AppTheme theme) => SetTheme(theme);
+
         private void SetTheme(AppTheme theme)
         {
             Resources = theme switch
@@ -28,6 +38,20 @@ namespace Xamarin.Neo4j
 
                 _ => new LightTheme()
             };
+
+            ApplyNavBarColors();
+            ThemeChanged?.Invoke(this, EventArgs.Empty);
+        }
+
+        // Called both from SetTheme and from MainActivity.OnResume so that
+        // theme changes while the app is backgrounded are picked up on return.
+        public void ApplyNavBarColors()
+        {
+            if (MainPage is NavigationPage navPage)
+            {
+                navPage.BarBackgroundColor = Color.FromArgb("#31333b");
+                navPage.BarTextColor = Colors.White;
+            }
         }
 
         protected override void OnStart()

Xamarin.Neo4j/Xamarin.Neo4j/Xamarin.Neo4j/Themes/DarkTheme.xaml

@@ -31,7 +31,7 @@
 
     <Style TargetType="TabbedPage" ApplyToDerivedTypes="True">
         <Setter Property="BackgroundColor" Value="White"/>
-        <Setter Property="BarTextColor" Value="Black"/>
+        <Setter Property="BarTextColor" Value="White"/>
         <Setter Property="SelectedTabColor" Value="White"/>
     </Style>
 

Xamarin.Neo4j/Xamarin.Neo4j/Xamarin.Neo4j/Themes/Fonts.xaml

@@ -4,18 +4,8 @@
                     xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
                     x:Class="Xamarin.Neo4j.Themes.Fonts">
 
-    <OnPlatform x:TypeArguments="x:String" x:Key="FontAwesomeBrands">
-        <On Platform="Android" Value="FontAwesome5Brands.ttf#Regular" />
-        <On Platform="iOS" Value="FontAwesome5Brands-Regular" />
-    </OnPlatform>
+    <x:String x:Key="FontAwesomeBrands">FontAwesome5Brands-Regular</x:String>
+    <x:String x:Key="FontAwesomeSolid">FontAwesome5Free-Solid</x:String>
+    <x:String x:Key="FontAwesomeRegular">FontAwesome5Free-Regular</x:String>
 
-    <OnPlatform x:TypeArguments="x:String" x:Key="FontAwesomeSolid">
-        <On Platform="Android" Value="FontAwesome5Solid.ttf#Regular" />
-        <On Platform="iOS" Value="FontAwesome5Free-Solid" />
-    </OnPlatform>
-
-    <OnPlatform x:TypeArguments="x:String" x:Key="FontAwesomeRegular">
-        <On Platform="Android" Value="FontAwesome5Regular.ttf#Regular" />
-        <On Platform="iOS" Value="FontAwesome5Free-Regular" />
-    </OnPlatform>
 </ResourceDictionary>

Xamarin.Neo4j/Xamarin.Neo4j/Xamarin.Neo4j/Themes/LightTheme.xaml

@@ -23,6 +23,15 @@
         <Setter Property="BackgroundColor" Value="Transparent" />
     </Style>
 
+    <Style TargetType="Entry" ApplyToDerivedTypes="True">
+        <Setter Property="TextColor" Value="Black" />
+        <Setter Property="PlaceholderColor" Value="#868a92" />
+    </Style>
+
+    <Style TargetType="Picker" ApplyToDerivedTypes="True">
+        <Setter Property="TextColor" Value="Black" />
+    </Style>
+
     <Style TargetType="NavigationPage">
         <Setter Property="BarBackgroundColor" Value="{StaticResource Accent}"/>
         <Setter Property="BarTextColor" Value="White" />