🔒 [security fix] Path Traversal in BrowserController and DownloadController

[juzaweb]

This PR fixes a security vulnerability that allowed path traversal in the file manager's showFile and getDownload endpoints.

🎯 What

The showFile and getDownload methods used user-supplied paths to access files on the storage disk without sufficient sanitization. This allowed an attacker to use ../ sequences to access files outside the intended storage root.

⚠️ Risk

An attacker could potentially read sensitive system files or other users' private files if the storage disk had access to them, leading to information disclosure.

🛡️ Solution

1. Centralized Sanitization: Added a cleanPath method to the base FileManagerController that:
   • Aborts with a 404 if the path contains .., preventing any traversal attempts.
   • Trims leading slashes and backslashes to ensure paths are relative to the disk root.
2. Refactored DownloadController: Updated DownloadController to extend FileManagerController and use the cleanPath logic.
3. Explicit Existence Check: Enhanced DownloadController::getDownload to verify file existence via Storage::exists($file) before attempting to retrieve the local path, ensuring that traversal attempts that bypass string checks (if any) are caught by the filesystem driver's own security boundaries.
4. Automated Testing: Added a new feature test tests/Feature/Security/PathTraversalTest.php covering standard traversal, nested bypass attempts (....//), and edge cases.

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PR created automatically by Jules for task 3829253760826571357 started by @juzaweb

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