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/openai-get-model.ts

@@ -0,0 +1,13 @@
+import {Command} from "../base/command";
+import {Message} from "typescript-telegram-bot-api";
+import {logError, replyToMessage} from "../util/utils";
+import {Environment} from "../common/environment";
+
+export class OpenAIGetModel extends Command {
+    title = "/openAIGetModel";
+    description = "Get current OpenAI model";
+
+    async execute(msg: Message): Promise<void> {
+        await replyToMessage({message: msg, text: `Текущая модель: "${Environment.OPENAI_MODEL}"`}).catch(logError);
+    }
+}