fix(cloud): use the same login method as the code request in cloud im…

[Jamie932]

First thanks a lot for this project - happy to have now be running fully local! Hit a snag whilst implementing it myself though, hence this PR.

The Issue

Cloud import on the admin page ("Send Code" → "Fetch Data") wouldn't accept any code I gave it, just Invalid code - check your code and try again. every time. I'm in the UK on the EU cloud. The response after sending the code also showed "country": "None", as a string, which was the first clue.

Why

The code gets sent one way and the login tries another:

• The admin page doesn't send a region, so the library looks the account up starting at usiot. For my account usiot comes back with countrycode=44 but no country, and because the lookup stops at the first answer with either, euiot never gets asked.
• With no country, request_code_v4() quietly falls back to the old v1 endpoint to send the code.
• request_code() then saved the country as str(None), so the string "None".
• submit_code() makes a new client pinned to euiot and calls code_login_v4 with country=session_data.country or None. Because the saved value is the text "None" rather than an actual None, the or None never kicks in and the login goes v4. Even with a proper None it'd still end up v4, because euiot does return a country (GB) when you ask it directly.
• The code was sent with v1 and the login uses v4, so Roborock rejects it with 2018.

HA's own Roborock setup doesn't hit this because it uses the same client for both steps, so it ends up v1/v1. It only breaks here because a second client works the country out again.

The fix

• Keep country as a proper None instead of the string "None".
• Remember which method actually sent the code (v1 or v4), using the same rule the library uses.
• In submit_code(), log in the same way: code_login() for v1, or code_login_v4() with the stored country/country_code for v4. Nothing gets looked up again.

The v4 path works the same as before, apart from using the stored values.

Testing

• Added tests to tests/test_cloud.py with a faked client, so no network:
  • No country on discovery: records v1, country is None, the login uses code_login, it doesn't look the country up again, and the device identifier carries over.
  • Normal case: v4 both ends with the stored values.
  • Unknown and expired sessions still raise ValueError.
  • Three of these fail on the old cloud.py, so they do catch it.
• uv run pytest -q passes, all 244.
• Tested it for real on my account with no region set. It sent the code via v1, logged in via v1 on euiot, and the import worked and found my vacuum. Before this, every code got rejected.
• I haven't been able to test the v4 path live, since my account doesn't take it. It's covered by the tests and only changes to use the stored values.

[Lash-L]

TY! Believe it or not, I have made this mistake historically when it comes to working with regions... Appreciate the PR!