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/Config.ps1

@@ -0,0 +1,127 @@
+# Config.ps1 — config.json and state.json read/write helpers
+# Requires $InternalRoot to be defined in the calling script's scope before dot-sourcing.
+
+function Get-ConfigPath { Join-Path $InternalRoot 'data\config.json' }
+function Get-StatePath  { Join-Path $InternalRoot 'data\state\state.json' }
+
+# ── Config ────────────────────────────────────────────────────────────────────
+
+function Get-Config {
+    $path = Get-ConfigPath
+    if (-not (Test-Path $path)) {
+        return @{ features = @{} }
+    }
+    try {
+        $raw = Get-Content -Path $path -Raw -Encoding UTF8 -ErrorAction Stop
+        return ConvertTo-DeepHashtable ($raw | ConvertFrom-Json)
+    }
+    catch {
+        Write-Log -Level Error -Message "Failed to read config.json, returning empty defaults: $_" -Feature 'Config'
+        return @{ features = @{} }
+    }
+}
+
+function Save-Config {
+    param([hashtable]$Config)
+
+    $path = Get-ConfigPath
+    $dir  = Split-Path $path -Parent
+    if (-not (Test-Path $dir)) {
+        New-Item -ItemType Directory -Path $dir -Force | Out-Null
+    }
+    try {
+        $Config | ConvertTo-Json -Depth 10 | Set-Content -Path $path -Encoding UTF8 -ErrorAction Stop
+    }
+    catch {
+        Write-Log -Level Error -Message "Failed to save config.json: $_" -Feature 'Config'
+    }
+}
+
+# ── State ─────────────────────────────────────────────────────────────────────
+
+function Get-State {
+    $path = Get-StatePath
+    if (-not (Test-Path $path)) {
+        return @{}
+    }
+    try {
+        $raw = Get-Content -Path $path -Raw -Encoding UTF8 -ErrorAction Stop
+        return ConvertTo-DeepHashtable ($raw | ConvertFrom-Json)
+    }
+    catch {
+        Write-Log -Level Error -Message "Failed to read state.json, returning empty state: $_" -Feature 'Config'
+        return @{}
+    }
+}
+
+function Save-State {
+    param([hashtable]$State)
+
+    $path = Get-StatePath
+    $dir  = Split-Path $path -Parent
+    if (-not (Test-Path $dir)) {
+        New-Item -ItemType Directory -Path $dir -Force | Out-Null
+    }
+    try {
+        $State | ConvertTo-Json -Depth 10 | Set-Content -Path $path -Encoding UTF8 -ErrorAction Stop
+    }
+    catch {
+        Write-Log -Level Error -Message "Failed to save state.json: $_" -Feature 'Config'
+    }
+}
+
+# ── Feature config seeding ────────────────────────────────────────────────────
+
+function Ensure-FeatureConfig {
+    <#
+    .SYNOPSIS
+        Ensures config.json contains an entry for the given feature, with all
+        settings keys present. Missing keys are filled from $FeatureMeta.Settings[*].Default.
+        Returns the (potentially modified) config hashtable.
+    #>
+    param(
+        [hashtable]$Config,
+        [hashtable]$FeatureMeta
+    )
+
+    $name = $FeatureMeta.Name
+
+    if (-not $Config.features.ContainsKey($name)) {
+        $Config.features[$name] = @{ enabled = $false }
+    }
+
+    foreach ($setting in $FeatureMeta.Settings) {
+        if (-not $Config.features[$name].ContainsKey($setting.Key)) {
+            $Config.features[$name][$setting.Key] = $setting.Default
+        }
+    }
+
+    return $Config
+}
+
+# ── Internal helper ───────────────────────────────────────────────────────────
+
+function ConvertTo-DeepHashtable {
+    <#
+    .SYNOPSIS
+        Recursively converts PSCustomObject (from ConvertFrom-Json) into hashtables
+        so all config/state values are mutable and support .ContainsKey().
+    #>
+    param([object]$InputObject)
+
+    if ($null -eq $InputObject)                                               { return $null }
+    if ($InputObject -is [hashtable])                                         { return $InputObject }
+    if ($InputObject -is [System.Collections.IEnumerable] -and
+        $InputObject -isnot [string]) {
+        return @($InputObject | ForEach-Object { ConvertTo-DeepHashtable $_ })
+    }
+    if ($InputObject -is [PSCustomObject]) {
+        $hash = @{}
+        foreach ($prop in $InputObject.PSObject.Properties) {
+            $hash[$prop.Name] = ConvertTo-DeepHashtable $prop.Value
+        }
+        return $hash
+    }
+    return $InputObject
+}
+