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/NetworkUtils.ps1

@@ -0,0 +1,35 @@
+# NetworkUtils.ps1 — network detection utilities
+# Requires $InternalRoot to be defined in the calling script's scope before dot-sourcing.
+
+function Test-DnsSuffixConnected {
+    <#
+    .SYNOPSIS
+        Returns $true if any currently UP network adapter has a connection-specific
+        DNS suffix that contains the specified suffix string.
+    #>
+    [CmdletBinding()]
+    [OutputType([bool])]
+    param(
+        [Parameter(Mandatory)]
+        [string]$Suffix
+    )
+
+    try {
+        $clients = Get-DnsClient -ErrorAction Stop
+        foreach ($client in $clients) {
+            if ($client.ConnectionSpecificSuffix -notlike "*$Suffix*") { continue }
+
+            # Verify the adapter is actually connected/up
+            $adapter = Get-NetAdapter -InterfaceIndex $client.InterfaceIndex -ErrorAction SilentlyContinue
+            if ($adapter -and $adapter.Status -eq 'Up') {
+                return $true
+            }
+        }
+        return $false
+    }
+    catch {
+        Write-Log -Level Warn -Message "DNS suffix check failed for '$Suffix': $_" -Feature 'NetworkUtils'
+        return $false
+    }
+}
+