Add ShellDemo sample with comprehensive XAML controls showcase

Complete ShellDemo application demonstrating all MAUI controls:
- App/AppShell: Shell navigation with flyout menu
- HomePage: Feature cards, theme toggle, quick actions
- ButtonsPage: Button styles, states, variations, event logging
- TextInputPage: Entry, Editor, SearchBar with keyboard shortcuts
- SelectionPage: CheckBox, Switch, Slider with colored variants
- PickersPage: Picker, DatePicker, TimePicker demos
- ListsPage: CollectionView with fruits, colors, contacts
- ProgressPage: ProgressBar, ActivityIndicator, interactive demo
- GridsPage: Grid layouts - auto/star/absolute sizing, spans, nesting
- AboutPage: OpenMaui Linux information
- DetailPage: Push/pop navigation demo

All pages use proper XAML with code-behind following MAUI patterns.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

samples/ShellDemo/Pages/TextInputPage.xaml

@@ -0,0 +1,91 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<ContentPage xmlns="http://schemas.microsoft.com/dotnet/2021/maui"
+             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
+             x:Class="ShellDemo.Pages.TextInputPage"
+             Title="Text Input"
+             BackgroundColor="{StaticResource PageBackground}">
+
+    <ScrollView>
+        <VerticalStackLayout Padding="20" Spacing="15">
+
+            <Label Text="Text Input Controls"
+                   FontSize="24"
+                   FontAttributes="Bold" />
+
+            <Label Text="Click on any field and start typing. All keyboard input is handled by the framework."
+                   FontSize="14"
+                   TextColor="{StaticResource TextSecondary}" />
+
+            <!-- Entry Section -->
+            <BoxView HeightRequest="1" Color="#E0E0E0" />
+            <Label Text="Entry (Single Line)" FontSize="18" FontAttributes="Bold" />
+
+            <Entry x:Name="NameEntry"
+                   Placeholder="Enter your name..."
+                   FontSize="14"
+                   TextChanged="OnNameEntryTextChanged" />
+            <Label x:Name="EntryOutput"
+                   FontSize="12"
+                   TextColor="{StaticResource TextSecondary}" />
+
+            <Entry Placeholder="Enter your email..."
+                   FontSize="14"
+                   Keyboard="Email" />
+            <Label Text="Email keyboard type"
+                   FontSize="12"
+                   TextColor="{StaticResource TextSecondary}" />
+
+            <Entry Placeholder="Enter password..."
+                   FontSize="14"
+                   IsPassword="True" />
+            <Label Text="Password field (text hidden)"
+                   FontSize="12"
+                   TextColor="{StaticResource TextSecondary}" />
+
+            <!-- SearchBar Section -->
+            <BoxView HeightRequest="1" Color="#E0E0E0" />
+            <Label Text="SearchBar" FontSize="18" FontAttributes="Bold" />
+
+            <SearchBar x:Name="DemoSearchBar"
+                       Placeholder="Search for items..."
+                       TextChanged="OnSearchTextChanged"
+                       SearchButtonPressed="OnSearchButtonPressed" />
+            <Label x:Name="SearchOutput"
+                   FontSize="12"
+                   TextColor="{StaticResource TextSecondary}" />
+
+            <!-- Editor Section -->
+            <BoxView HeightRequest="1" Color="#E0E0E0" />
+            <Label Text="Editor (Multi-line)" FontSize="18" FontAttributes="Bold" />
+
+            <Editor x:Name="DemoEditor"
+                    Placeholder="Enter multiple lines of text here...&#10;Press Enter to create new lines."
+                    HeightRequest="120"
+                    FontSize="14"
+                    TextChanged="OnEditorTextChanged" />
+            <Label x:Name="EditorOutput"
+                   FontSize="12"
+                   TextColor="{StaticResource TextSecondary}" />
+
+            <!-- Keyboard Shortcuts Info -->
+            <BoxView HeightRequest="1" Color="#E0E0E0" />
+            <Border BackgroundColor="#E3F2FD"
+                    Padding="15"
+                    StrokeThickness="0">
+                <Border.StrokeShape>
+                    <RoundRectangle CornerRadius="8" />
+                </Border.StrokeShape>
+                <VerticalStackLayout Spacing="5">
+                    <Label Text="Keyboard Shortcuts" FontAttributes="Bold" />
+                    <Label Text="Ctrl+A: Select all" />
+                    <Label Text="Ctrl+C: Copy" />
+                    <Label Text="Ctrl+V: Paste" />
+                    <Label Text="Ctrl+X: Cut" />
+                    <Label Text="Home/End: Move to start/end" />
+                    <Label Text="Shift+Arrow: Select text" />
+                </VerticalStackLayout>
+            </Border>
+
+        </VerticalStackLayout>
+    </ScrollView>
+</ContentPage>