Add super-admin Administration section and restructure global vs company settings

- Add Administration sidebar section (super-admin only) with Companies, Users, and Global Settings pages
- Add super-admin middleware, controllers, and API routes under /api/v1/super-admin/
- Allow super-admins to manage all companies and users across tenants
- Add user impersonation with short-lived tokens, audit logging, and UI banner
- Move system-level settings (Mail, PDF, Backup, Update, File Disk) from per-company to Administration > Global Settings
- Convert save_pdf_to_disk from CompanySetting to global Setting
- Add per-company mail configuration overrides (optional, falls back to global)
- Add CompanyMailConfigService to apply company mail config before sending emails

app/Http/Requests/AdminUserUpdateRequest.php

@@ -0,0 +1,28 @@
+<?php
+
+namespace App\Http\Requests;
+
+use Illuminate\Foundation\Http\FormRequest;
+use Illuminate\Validation\Rule;
+
+class AdminUserUpdateRequest extends FormRequest
+{
+    public function authorize(): bool
+    {
+        return $this->user()->isSuperAdmin();
+    }
+
+    public function rules(): array
+    {
+        return [
+            'name' => ['required', 'string'],
+            'email' => [
+                'required',
+                'email',
+                Rule::unique('users')->ignore($this->route('user')),
+            ],
+            'phone' => ['nullable', 'string'],
+            'password' => ['nullable', 'string', 'min:8'],
+        ];
+    }
+}