Fail explicitly when filesystem storage writes do not succeed

[javihgil]

Problem

FilesystemStorageDriver ignores write failures when creating directories and copying files.

Current code:

• src/Storage/FilesystemStorageDriver.php:22 calls mkdir() without checking the result
• src/Storage/FilesystemStorageDriver.php:26 calls copy() without checking the result

Impact

The storage driver can report a stored file path even when the file was never written successfully.

That makes failures harder to detect and can leave the database pointing to files that do not exist.

Expected behavior

• validate directory creation and file copy operations
• throw a storage exception when the write fails
• keep the returned stored path only for successful writes