Add new features: DefaultBrowser, DynamicLock, SandwichReminder

- Implemented DefaultBrowser feature to notify users when the default browser does not match the configured app.
- Added DynamicLock feature to disable Dynamic Lock while connected to a specific network and re-enable it after disconnecting.
- Created SandwichReminder feature to prompt users to order a sandwich during work hours based on network and time settings.

Introduced helper libraries for configuration, elevation, logging, network utilities, and toast notifications.

- Config.ps1: Added functions for reading and writing configuration and state files.
- Elevation.ps1: Added functions to check for administrator privileges and request elevation.
- Logging.ps1: Implemented a shared logging utility for consistent logging across features.
- NetworkUtils.ps1: Added a function to check for DNS suffix connectivity.
- ToastHelper.ps1: Created a helper for displaying Windows toast notifications.

Implemented runner.ps1 as the main entry point for executing features based on configuration.

internal/lib/ToastHelper.ps1

@@ -0,0 +1,81 @@
+# ToastHelper.ps1 — Windows toast notification helper (WinRT, no external modules)
+# Requires $InternalRoot to be defined in the calling script's scope before dot-sourcing.
+
+function Show-ToastNotification {
+    <#
+    .SYNOPSIS
+        Shows a Windows toast notification with optional action buttons.
+
+    .PARAMETER Buttons
+        Array of hashtables with keys:
+          Label  — button text
+          Action — URI to invoke (http://, https://, ms-settings:, etc.)
+                   Use empty string or 'dismiss' for a dismiss button.
+    #>
+    [CmdletBinding()]
+    param(
+        [Parameter(Mandatory)]
+        [string]$Title,
+
+        [Parameter(Mandatory)]
+        [string]$Body,
+
+        [object[]]$Buttons = @()
+    )
+
+    try {
+        # Load WinRT types.
+        # Note: [TypeName, Assembly, ContentType=WindowsRuntime] is valid PowerShell 5.1+ syntax
+        # for WinRT interop. Static parsers may flag it as an error — this is a known false positive.
+        [Windows.UI.Notifications.ToastNotificationManager, Windows.UI.Notifications, ContentType = WindowsRuntime] | Out-Null
+        [Windows.Data.Xml.Dom.XmlDocument, Windows.Data.Xml.Dom.XmlDocument, ContentType = WindowsRuntime] | Out-Null
+
+        # Use PowerShell's own AUMID — registered in Start Menu, ensures toast delivery
+        $AppId = '{1AC14E77-02E7-4E5D-B744-2EB1AE5198B7}\WindowsPowerShell\v1.0\powershell.exe'
+
+        # Build actions XML
+        $actionsXml = ''
+        if ($Buttons.Count -gt 0) {
+            $actionsXml = '<actions>'
+            foreach ($btn in $Buttons) {
+                $label  = [System.Security.SecurityElement]::Escape($btn.Label)
+                $isDismiss = ([string]$btn.Action -eq '' -or [string]$btn.Action -eq 'dismiss')
+
+                if ($isDismiss) {
+                    $actionsXml += "<action content=""$label"" arguments=""dismiss"" activationType=""system""/>"
+                } else {
+                    $action         = [System.Security.SecurityElement]::Escape($btn.Action)
+                    $activationType = 'protocol'   # covers http://, https://, ms-settings:, etc.
+                    $actionsXml    += "<action content=""$label"" arguments=""$action"" activationType=""$activationType""/>"
+                }
+            }
+            $actionsXml += '</actions>'
+        }
+
+        $escapedTitle = [System.Security.SecurityElement]::Escape($Title)
+        $escapedBody  = [System.Security.SecurityElement]::Escape($Body)
+
+        $toastXml = @"
+<toast>
+  <visual>
+    <binding template="ToastGeneric">
+      <text>$escapedTitle</text>
+      <text>$escapedBody</text>
+    </binding>
+  </visual>
+  $actionsXml
+</toast>
+"@
+        $xml = New-Object Windows.Data.Xml.Dom.XmlDocument
+        $xml.LoadXml($toastXml)
+
+        $toast = New-Object Windows.UI.Notifications.ToastNotification $xml
+        [Windows.UI.Notifications.ToastNotificationManager]::CreateToastNotifier($AppId).Show($toast)
+
+        Write-Log -Level Info -Message "Toast shown: '$Title'" -Feature 'ToastHelper'
+    }
+    catch {
+        Write-Log -Level Error -Message "Failed to show toast '$Title': $_" -Feature 'ToastHelper'
+    }
+}
+