feat(openai): add chat streaming and model commands

- add /openai (/chatgpt) chat command using OpenAI Responses API (streaming + incremental edits)
- add /openAIListModels, /openAIGetModel, /openAISetModel
- introduce base Command class and migrate non-chat commands to it
- wire OpenAI client + env vars (OPENAI_API_KEY, OPENAI_MODEL)
- bump deps (@google/genai, systeminformation, @types/node) and add openai

src/commands/mistral-chat.ts

@@ -1,4 +1,3 @@
-import {ChatCommand} from "../base/chat-command";
 import {Requirements} from "../base/requirements";
 import {Requirement} from "../base/requirement";
 import {Message} from "typescript-telegram-bot-api";
@@ -12,6 +11,7 @@ import {
 import {Environment} from "../common/environment";
 import {bot, mistralAi} from "../index";
 import {MessageStore} from "../common/message-store";
+import {ChatCommand} from "../base/chat-command";
 
 export class MistralChat extends ChatCommand {
     command = "mistral";