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>

app/Models/ScheduledTask.php

@@ -29,6 +29,11 @@ class ScheduledTask extends BaseModel
 
     protected $guarded = [];
 
+    public static function ownedByCurrentTeamAPI(int $teamId)
+    {
+        return static::where('team_id', $teamId)->orderBy('created_at', 'desc');
+    }
+
     protected function casts(): array
     {
         return [