feat: add UserResource with is_admin toggle and delete

User management resource with editable is_admin field, postcode support,
admin filter, and inline delete action. Includes list and edit pages.

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

app/Filament/NavigationGroup.php

@@ -0,0 +1,35 @@
+<?php
+
+namespace App\Filament;
+
+use BackedEnum;
+use Filament\Support\Contracts\HasIcon;
+use Filament\Support\Contracts\HasLabel;
+use Illuminate\Contracts\Support\Htmlable;
+
+enum NavigationGroup implements HasIcon, HasLabel
+{
+    case Users;
+
+    case Data;
+
+    case System;
+
+    public function getLabel(): string
+    {
+        return match ($this) {
+            self::Users => 'Users',
+            self::Data => 'Data',
+            self::System => 'System',
+        };
+    }
+
+    public function getIcon(): string|BackedEnum|Htmlable|null
+    {
+        return match ($this) {
+            self::Users => 'heroicon-o-users',
+            self::Data => 'heroicon-o-circle-stack',
+            self::System => 'heroicon-o-cog-6-tooth',
+        };
+    }
+}