Fix critical race condition in permission loading for concurrent environments

[imhayatunnabi]

This PR fixes a critical race condition vulnerability in the PermissionRegistrar class that affects applications running in concurrent environments (Laravel Octane, Swoole, RoadRunner, etc.).

Problem

The loadPermissions() method had a Time-of-Check to Time-of-Use (TOCTOU) race condition where multiple concurrent requests could simultaneously pass the if ($this->permissions) check before any of them loaded the permissions, causing:

1. Cache Stampede - Multiple simultaneous expensive database queries
2. Performance Degradation - Redundant operations under high load
3. Memory Waste - Multiple copies of permission data in memory
4. Database Overload - Excessive queries during cache refresh

Solution

Implemented a thread-safe double-checked locking pattern:

• Fast path check: Quick return if permissions already loaded
• Loading flag: $isLoadingPermissions prevents concurrent loading
• Wait & retry: Competing threads wait 10ms and recheck
• Double-check locking: Verify permissions not loaded by another thread
• Exception safety: try-finally ensures flag is always released

Code Changes

File: src/PermissionRegistrar.php

1. Added private bool $isLoadingPermissions = false; property
2. Enhanced loadPermissions() with thread-safe implementation
3. Updated clearPermissionsCollection() to reset the loading flag