Implement buy flow and migrate DTOs to schemas

Move DTO definitions from dto/ to schemas/ and update imports.
Add buy handler with FSM state management for device selection,
whitelist toggling, and duration choice. Include pricing logic,
inline keyboards, and new configuration fields.

keyboards/client.py

@@ -1,6 +1,10 @@
 from aiogram.types import InlineKeyboardButton, InlineKeyboardMarkup
 from aiogram.utils.keyboard import InlineKeyboardBuilder
 
+from config import settings
+from misc.utils import convert_duration_to_int
+from schemas.subscriptions import SubscriptionDuration
+
 main_menu: InlineKeyboardMarkup = InlineKeyboardBuilder(
     [
         [
@@ -14,6 +18,71 @@ main_menu: InlineKeyboardMarkup = InlineKeyboardBuilder(
     ]
 ).as_markup()
 
+_return_to_menu_btn: InlineKeyboardButton = InlineKeyboardButton(
+    text="⬅️ Назад", callback_data="menu:main"
+)
+
+
+def _return_btn(
+    data: str = "menu:main", text: str = "⬅️ Назад"
+) -> InlineKeyboardButton:
+    return InlineKeyboardButton(text=text, callback_data=data)
+
+
 return_to_menu: InlineKeyboardMarkup = InlineKeyboardBuilder(
-    [[InlineKeyboardButton(text="⬅️ Назад", callback_data="menu:main")]]
+    [[_return_to_menu_btn]]
 ).as_markup()
+
+
+def devices_selector(current: int = settings.min_devices, whitelists: bool = False):
+    builder = InlineKeyboardBuilder()
+
+    buttons = [
+        InlineKeyboardButton(
+            text=f"{'✅ ' if i == current else ''}{i}", callback_data=f"devices:{i}"
+        )
+        for i in range(settings.min_devices, settings.max_devices + 1)
+    ]
+    builder.add(*buttons).adjust(6)
+
+    wl_icon = "✅ " if whitelists else ""
+    builder.row(
+        InlineKeyboardButton(
+            text=f"{wl_icon}Обход Белых Списков (+100₽)",
+            callback_data="whitelist:toggle",
+        )
+    )
+    builder.row(InlineKeyboardButton(text="🟢", callback_data="confirm"))
+    builder.row(_return_to_menu_btn)
+
+    return builder.as_markup()
+
+
+def duration_selector(
+    current: SubscriptionDuration = SubscriptionDuration.MONTH,
+    back_cb: str = "menu:main",
+) -> InlineKeyboardMarkup:
+    builder = InlineKeyboardBuilder()
+    duration_int = convert_duration_to_int(current)
+
+    durations = [
+        (1, "1 Месяц"),
+        (3, "3 Месяца"),
+        (6, "6 Месяцев"),
+        (12, "1 Год"),
+    ]
+
+    for val, label in durations:
+        is_selected = val == duration_int
+
+        builder.button(
+            text=f"{'✅ ' if is_selected else ''}{label}",
+            callback_data=f"duration:{val}",
+        )
+
+    builder.row(
+        InlineKeyboardButton(text="🛒 Перейти к оплате", callback_data="confirm")
+    )
+    builder.row(_return_btn(back_cb))
+
+    return builder.as_markup()