fix(api): improve scheduled tasks API with auth, validation, and execution endpoints

- Add authorization checks ($this->authorize) for all read/write operations
- Use customApiValidator() instead of Validator::make() to match codebase patterns
- Add extra field rejection to prevent mass assignment
- Use Application::ownedByCurrentTeamAPI() for consistent query patterns
- Remove non-existent standalone_postgresql_id from hidden fields
- Add execution listing endpoints for both applications and services
- Add ScheduledTaskExecution OpenAPI schema
- Use $request->only() instead of $request->all() for safe updates
- Add ScheduledTaskFactory and feature tests

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

database/factories/ScheduledTaskFactory.php

@@ -0,0 +1,20 @@
+<?php
+
+namespace Database\Factories;
+
+use Illuminate\Database\Eloquent\Factories\Factory;
+
+class ScheduledTaskFactory extends Factory
+{
+    public function definition(): array
+    {
+        return [
+            'name' => fake()->word(),
+            'command' => 'echo hello',
+            'frequency' => '* * * * *',
+            'timeout' => 300,
+            'enabled' => true,
+            'team_id' => 1,
+        ];
+    }
+}