Add typing_extensions to pyproject.toml

[scottstanie]

Currently this is missing from the stated requirements, so running an isolated environment fails to import:

$ uvx --from capella-console-client python
Python 3.13.5 (main, Jun 12 2025, 12:22:43) [Clang 20.1.4 ] on darwin
Type "help", "copyright", "credits" or "license" for more information.

>>> import capella_console_client
Traceback (most recent call last):
  File "<python-input-0>", line 1, in <module>
    import capella_console_client
  File "/Users/staniewi/repos/console-client/capella_console_client/__init__.py", line 1, in <module>
    from .client import CapellaConsoleClient
  File "/Users/staniewi/repos/console-client/capella_console_client/client.py", line 8, in <module>
    from capella_console_client.s3 import S3Path
  File "/Users/staniewi/repos/console-client/capella_console_client/s3.py", line 5, in <module>
    from typing_extensions import TypeAlias
ModuleNotFoundError: No module named 'typing_extensions'

[coveralls]

coverage: 95.135%. remained the same
when pulling ef96184 on fix-missing-typing-extensions
into ea645ad on main.