Add extensive controller and model tests

tests/Feature/SystemUpdateControllerTest.php

@@ -0,0 +1,29 @@
+<?php
+
+use App\Models\Role;
+use App\Models\User;
+use Laravel\Sanctum\Sanctum;
+
+it('forbids system update for non-admins', function (): void {
+    $user = User::factory()->create();
+
+    Sanctum::actingAs($user);
+    $response = $this->postJson('/api/system/update');
+
+    $response->assertStatus(403);
+});
+
+it('returns validation error when gitea config is missing', function (): void {
+    putenv('GITEA_OWNER=');
+    putenv('GITEA_REPO=');
+
+    $admin = User::factory()->create();
+    $role = Role::firstOrCreate(['name' => 'ROLE_ADMIN'], ['color' => '#111111']);
+    $admin->roles()->attach($role);
+
+    Sanctum::actingAs($admin);
+    $response = $this->postJson('/api/system/update');
+
+    $response->assertStatus(422);
+    $response->assertJsonFragment(['message' => 'Missing Gitea configuration.']);
+});