Fix incorrect type annotations in OpenApiV1 plant_id and plant_list

[johanzander]

Closes #157.

1. V1 plant_id annotations

GrowattApi annotates plant_id as str on every method that takes one, but OpenApiV1 annotates it as int on plant_details, plant_energy_overview, plant_power_overview, plant_energy_history and device_list.

All five only pass the value through to params={"plant_id": plant_id}, so str has always worked at runtime — only the annotation disagreed. Since 2.2.0 shipped py.typed, the mismatch is now visible to consumers: a caller holding a plant id as a str (which is what the base class returns, and what the ID naturally is) must either suppress arg-type errors or coerce with int() — and coercing crashes on non-numeric ids.

The # type: ignore[override] on device_list is left in place — it covers the return type differing from the base class (dict vs list), which is unrelated to plant_id.

2. plant_list empty-case return

#153 corrected the plant_list annotation to dict[str, Any], but the fallback when the response has no back key is still []:

def plant_list(self, user_id: str) -> dict[str, Any]:
    ...
    return response.json().get("back", [])

So the empty case returns a list and contradicts the annotation. A caller that follows the annotation and does plant_info.get("data") hits an AttributeError on that path, which forces an isinstance() guard purely to defend against the default. plant_detail, on the same endpoint family, already defaults to {}.

Scope

Both changes are annotation-consistency fixes; the only runtime change is the {} default in the empty-response path, which replaces an AttributeError with a falsy dict.

Release note

Together with #153 — merged but unreleased, as 2.2.0 shipped one day before it landed — this unblocks removing the remaining type suppressions and defensive guards in the Home Assistant growatt_server integration (home-assistant/core#173220). Verified locally: with this branch installed, that integration's # type: ignore[arg-type] comments delete cleanly with mypy passing and its full test suite green. A 2.3.0 covering both PRs would let those changes land.

[indykoning]

Simple, and looks good!

[johanzander]

great! looking forward to the next release!