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/dice.ts

@@ -1,4 +1,4 @@
-import {ChatCommand} from "../base/chat-command";
+import {Command} from "../base/command";
 import {Message} from "typescript-telegram-bot-api";
 import {logError, randomValue} from "../util/utils";
 import {bot} from "../index";
@@ -6,7 +6,7 @@ import {bot} from "../index";
 type DiceEmoji = "🎲" | "🎯" | "🏀" | "⚽" | "🎳" | "🎰";
 const emojis = ["🎲", "🎯", "🏀", "⚽", "🎳", "🎰"];
 
-export class Dice extends ChatCommand {
+export class Dice extends Command {
     title = "/dice";
     description = "Sends random or specific dice";