Mi Home cloud: reuse stored passToken via login cookies

[jeeves-butler-co]

This is a smaller version of #1683 that keeps the part Tasshack identified as valid and removes the unsupported refresh-token flow and timeout/retry changes.

Changes:

• Store passToken as an optional 5th field in auth_key.
• Inject stored passToken/userId into the Mi Home login session cookies before serviceLogin.
• If serviceLogin returns an STS location from the stored cookie, skip password/2FA and proceed directly to login_step_3().
• Preserve existing timeout/retry/check_login behavior.

Validation:

• python3 -m py_compile custom_components/dreame_vacuum/dreame/protocol.py

Context: derived from the discussion in #1683.

[Tasshack]

@jeeves-butler-co have you tested this?

[jeeves-butler-co]

Not end-to-end against a real Mi Home account/service-token-expiration case.

What I tested:

• syntax/import-level validation with python3 -m py_compile custom_components/dreame_vacuum/dreame/protocol.py;
• diff review to make sure this PR only stores/reuses passToken through cookies and does not change timeout/retry/check_login behavior.

So this should be treated as an unverified implementation of the cookie flow you described, not as a confirmed fix. If you prefer not to keep untested PRs open, I can close it.

[Tasshack]

As I said before, it is very hard for me to test this on a solid fiber connection on a half static ip but I will give it a try anyway...