fix(encryption): Fix type error for unencryptedSize property

The Stream\Encryption::$unencryptedSize property was typed as ?int,
but fixUnencryptedSize() returns int|float for large files. This
caused TypeErrors when the verifyUnencryptedSize() fix triggered
recalculation.

Changed property type from ?int to int|float|null to match the
return type of fixUnencryptedSize().

Fixes:
- EncryptionMasterKeyUploadTest::testUploadOverWrite
- EncryptionUploadTest::testUploadOverWrite

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 (1M context) <[email protected]>
Signed-off-by: Stephen Cuppett <[email protected]>

Author: cuppett

lib/private/Files/Stream/Encryption.php

@@ -28,7 +28,7 @@ class Encryption extends Wrapper {
 	protected string $cache;
 	protected ?int $size = null;
 	protected int $position;
-	protected ?int $unencryptedSize = null;
+	protected int|float|null $unencryptedSize = null;
 	protected int $headerSize;
 	protected int $unencryptedBlockSize;
 	protected array $header;