Fix optional CallbackQuery message parsing

[Royna2544]

Motivation

• Prevent a crash/DoS during JSON parsing by avoiding unchecked nlohmann::json::operator[] access for the optional CallbackQuery::message field.

Description

• Replace the unsafe result->message = parse(data["message"]); with the key-aware helper result->message = parse<MaybeInaccessibleMessage>(data, "message"); in src/types/CallbackQuery.cpp to yield std::nullopt when the key is absent.

Testing

• No automated tests were executed because a full CMake/build could not be run due to missing nlohmann_json development files and restricted network access preventing dependency retrieval; the change is intentionally minimal and follows the existing key-aware parsing pattern used elsewhere.

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Codex Task