feat: implement adapter/telegram/ with aiogram 3.x

Virtual DM chats, FSM (idle/waiting_response/settings states),
SQLite local DB for tg_users+chats, converter, keyboards, and
handlers for /start, /new, /chats, /settings, confirm callbacks.

adapter/telegram/keyboards/chat.py

@@ -0,0 +1,16 @@
+# adapter/telegram/keyboards/chat.py
+from __future__ import annotations
+
+from aiogram.types import InlineKeyboardButton, InlineKeyboardMarkup
+
+
+def chats_list_keyboard(chats: list[dict], active_chat_id: str | None) -> InlineKeyboardMarkup:
+    buttons = []
+    for chat in chats:
+        mark = "● " if chat["chat_id"] == active_chat_id else ""
+        buttons.append([InlineKeyboardButton(
+            text=f"{mark}{chat['name']}",
+            callback_data=f"switch:{chat['chat_id']}:{chat['name']}",
+        )])
+    buttons.append([InlineKeyboardButton(text="➕ Новый чат", callback_data="new_chat")])
+    return InlineKeyboardMarkup(inline_keyboard=buttons)