feat(bot): add chat proxy

backend/src/bot/handlers/proxy/handler.py

@@ -0,0 +1,101 @@
+from dataclasses import dataclass
+
+from aiogram import Bot, Router, types
+from aiogram.client.default import DefaultBotProperties
+from aiogram.enums import ParseMode
+from aiogram.filters import Command
+
+router = Router()
+
+
+@dataclass
+class ProxyConfig:
+    bot_token: str
+    target_chat_id: int
+    proxy_bot: Bot
+
+
+proxy_states: dict[int, ProxyConfig] = {}
+
+
+def get_proxy_config(chat_id: int) -> ProxyConfig | None:
+    return proxy_states.get(chat_id)
+
+
+async def cleanup_proxy(chat_id: int) -> None:
+    config = proxy_states.pop(chat_id, None)
+    if config:
+        await config.proxy_bot.session.close()
+
+
+@router.message(Command("proxy"))
+async def on_proxy(message: types.Message) -> None:  # noqa: C901
+    if not message.from_user or not message.text:
+        return
+
+    chat_id = message.chat.id
+    args = message.text.split(maxsplit=2)
+
+    if len(args) == 1:
+        config = get_proxy_config(chat_id)
+        if config:
+            await message.answer(
+                f"Proxy active → chat {config.target_chat_id}\n\n"
+                "Use /proxy deactivate to stop."
+            )
+        else:
+            await message.answer(
+                "Usage:\n"
+                "/proxy BOT_TOKEN CHAT_ID - activate proxy\n"
+                "/proxy deactivate - stop proxy"
+            )
+        return
+
+    if args[1].lower() == "deactivate":
+        if chat_id in proxy_states:
+            await cleanup_proxy(chat_id)
+            await message.answer("✓ Proxy deactivated.")
+        else:
+            await message.answer("No active proxy.")
+        return
+
+    if len(args) < 3:  # noqa: PLR2004
+        await message.answer("Usage: /proxy BOT_TOKEN CHAT_ID")
+        return
+
+    bot_token = args[1]
+    try:
+        target_chat_id = int(args[2])
+    except ValueError:
+        await message.answer("Invalid chat ID. Must be a number.")
+        return
+
+    if chat_id in proxy_states:
+        await cleanup_proxy(chat_id)
+
+    try:
+        proxy_bot = Bot(
+            token=bot_token, default=DefaultBotProperties(parse_mode=ParseMode.HTML)
+        )
+        bot_info = await proxy_bot.get_me()
+
+        try:
+            await proxy_bot.send_message(target_chat_id, "🔗 Proxy connected")
+        except Exception as e:  # noqa: BLE001
+            await proxy_bot.session.close()
+            await message.answer(f"Cannot send to chat {target_chat_id}: {e}")
+            return
+
+        proxy_states[chat_id] = ProxyConfig(
+            bot_token=bot_token, target_chat_id=target_chat_id, proxy_bot=proxy_bot
+        )
+
+        await message.answer(
+            f"✓ Proxy activated via @{bot_info.username}\n"
+            f"Target: {target_chat_id}\n\n"
+            "All messages will be forwarded."
+        )
+        await message.delete()
+
+    except Exception as e:  # noqa: BLE001
+        await message.answer(f"Invalid bot token: {e}")