Add missing types to Endpoints\Keys

[Strift]

The Keys endpoint class requires updates to handle array shapes and return types more explicitly.

File: src/Endpoints/Keys.php

Action:

• newInstance(array $attributes): Add specific PHPDoc array shape.
• fill(array $attributes): Add specific PHPDoc array shape.
• create(array $options = []): Add PHPDoc defining expected $options.
• update(string $keyOrUid, array $options = []): Add PHPDoc defining expected $options.
• allRaw(array $options = []): Add PHPDoc for input and output array shapes.
• getActions(): Update return PHPDoc to @return list<string>|null.
• getIndexes(): Update return PHPDoc to @return list<string>|null.