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/prefix-response.ts

@@ -1,9 +1,9 @@
-import {ChatCommand} from "../base/chat-command";
+import {Command} from "../base/command";
 import {Message} from "typescript-telegram-bot-api";
 import {logError, randomValue, replyToMessage} from "../util/utils";
 import {Environment} from "../common/environment";
 
-export class PrefixResponse extends ChatCommand {
+export class PrefixResponse extends Command {
     async execute(msg: Message): Promise<void> {
         await replyToMessage({message: msg, text: randomValue(Environment.ANSWERS.prefix)}).catch(logError);
     }