feat: add Telegram configuration to settings (issue #33)

Add Telegram notification configuration:
- src/config.py: Add TELEGRAM_BOT_TOKEN, TELEGRAM_CHAT_ID, TELEGRAM_ENABLED
- .env.example: Add Telegram section with setup instructions

Fields added after S3_REGION (line 55).
Follows existing optional API pattern (NEWS_API_KEY, etc.).
No breaking changes to existing settings.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

.env.example

@@ -26,3 +26,10 @@ MODE=paper
 # NEWS_API_KEY=your_news_api_key_here
 # NEWS_API_PROVIDER=alphavantage
 # MARKET_DATA_API_KEY=your_market_data_key_here
+
+# Telegram Notifications (optional)
+# Get bot token from @BotFather on Telegram
+# Get chat ID from @userinfobot or your chat
+# TELEGRAM_BOT_TOKEN=1234567890:ABCdefGHIjklMNOpqrsTUVwxyz
+# TELEGRAM_CHAT_ID=123456789
+# TELEGRAM_ENABLED=true

src/config.py

@@ -54,6 +54,11 @@ class Settings(BaseSettings):
     S3_BUCKET_NAME: str | None = None
     S3_REGION: str = "us-east-1"
 
+    # Telegram Notifications (optional)
+    TELEGRAM_BOT_TOKEN: str | None = None
+    TELEGRAM_CHAT_ID: str | None = None
+    TELEGRAM_ENABLED: bool = True
+
     model_config = {"env_file": ".env", "env_file_encoding": "utf-8"}
 
     @property

tests/test_telegram.py

@@ -0,0 +1,269 @@
+"""Tests for Telegram notification client."""
+
+from unittest.mock import AsyncMock, patch
+
+import aiohttp
+import pytest
+
+from src.notifications.telegram_client import NotificationPriority, TelegramClient
+
+
+class TestTelegramClientInit:
+    """Test client initialization scenarios."""
+
+    def test_disabled_via_flag(self) -> None:
+        """Client disabled via enabled=False flag."""
+        client = TelegramClient(
+            bot_token="123:abc", chat_id="456", enabled=False
+        )
+        assert client._enabled is False
+
+    def test_disabled_missing_token(self) -> None:
+        """Client disabled when bot_token is None."""
+        client = TelegramClient(bot_token=None, chat_id="456", enabled=True)
+        assert client._enabled is False
+
+    def test_disabled_missing_chat_id(self) -> None:
+        """Client disabled when chat_id is None."""
+        client = TelegramClient(bot_token="123:abc", chat_id=None, enabled=True)
+        assert client._enabled is False
+
+    def test_enabled_with_credentials(self) -> None:
+        """Client enabled when credentials provided."""
+        client = TelegramClient(
+            bot_token="123:abc", chat_id="456", enabled=True
+        )
+        assert client._enabled is True
+
+
+class TestNotificationSending:
+    """Test notification sending behavior."""
+
+    @pytest.mark.asyncio
+    async def test_no_send_when_disabled(self) -> None:
+        """Notifications not sent when client disabled."""
+        client = TelegramClient(enabled=False)
+
+        with patch("aiohttp.ClientSession.post") as mock_post:
+            await client.notify_trade_execution(
+                stock_code="AAPL",
+                market="United States",
+                action="BUY",
+                quantity=10,
+                price=150.0,
+                confidence=85.0,
+            )
+            mock_post.assert_not_called()
+
+    @pytest.mark.asyncio
+    async def test_trade_execution_format(self) -> None:
+        """Trade notification has correct format."""
+        client = TelegramClient(
+            bot_token="123:abc", chat_id="456", enabled=True
+        )
+
+        mock_resp = AsyncMock()
+        mock_resp.status = 200
+        mock_resp.__aenter__ = AsyncMock(return_value=mock_resp)
+        mock_resp.__aexit__ = AsyncMock(return_value=False)
+
+        with patch("aiohttp.ClientSession.post", return_value=mock_resp) as mock_post:
+            await client.notify_trade_execution(
+                stock_code="TSLA",
+                market="United States",
+                action="SELL",
+                quantity=5,
+                price=250.50,
+                confidence=92.0,
+            )
+
+            # Verify API call was made
+            assert mock_post.call_count == 1
+            call_args = mock_post.call_args
+
+            # Check payload structure
+            payload = call_args.kwargs["json"]
+            assert payload["chat_id"] == "456"
+            assert "TSLA" in payload["text"]
+            assert "SELL" in payload["text"]
+            assert "5" in payload["text"]
+            assert "250.50" in payload["text"]
+            assert "92%" in payload["text"]
+
+    @pytest.mark.asyncio
+    async def test_circuit_breaker_priority(self) -> None:
+        """Circuit breaker uses CRITICAL priority."""
+        client = TelegramClient(
+            bot_token="123:abc", chat_id="456", enabled=True
+        )
+
+        mock_resp = AsyncMock()
+        mock_resp.status = 200
+        mock_resp.__aenter__ = AsyncMock(return_value=mock_resp)
+        mock_resp.__aexit__ = AsyncMock(return_value=False)
+
+        with patch("aiohttp.ClientSession.post", return_value=mock_resp) as mock_post:
+            await client.notify_circuit_breaker(pnl_pct=-3.15, threshold=-3.0)
+
+            payload = mock_post.call_args.kwargs["json"]
+            # CRITICAL priority has 🚨 emoji
+            assert NotificationPriority.CRITICAL.emoji in payload["text"]
+            assert "-3.15%" in payload["text"]
+
+    @pytest.mark.asyncio
+    async def test_api_error_handling(self) -> None:
+        """API errors logged but don't crash."""
+        client = TelegramClient(
+            bot_token="123:abc", chat_id="456", enabled=True
+        )
+
+        mock_resp = AsyncMock()
+        mock_resp.status = 400
+        mock_resp.text = AsyncMock(return_value="Bad Request")
+        mock_resp.__aenter__ = AsyncMock(return_value=mock_resp)
+        mock_resp.__aexit__ = AsyncMock(return_value=False)
+
+        with patch("aiohttp.ClientSession.post", return_value=mock_resp):
+            # Should not raise exception
+            await client.notify_system_start(mode="paper", enabled_markets=["KR"])
+
+    @pytest.mark.asyncio
+    async def test_timeout_handling(self) -> None:
+        """Timeouts logged but don't crash."""
+        client = TelegramClient(
+            bot_token="123:abc", chat_id="456", enabled=True
+        )
+
+        with patch(
+            "aiohttp.ClientSession.post",
+            side_effect=aiohttp.ClientError("Connection timeout"),
+        ):
+            # Should not raise exception
+            await client.notify_error(
+                error_type="Test Error", error_msg="Test", context="test"
+            )
+
+    @pytest.mark.asyncio
+    async def test_session_management(self) -> None:
+        """Session created and reused correctly."""
+        client = TelegramClient(
+            bot_token="123:abc", chat_id="456", enabled=True
+        )
+
+        # Session should be None initially
+        assert client._session is None
+
+        mock_resp = AsyncMock()
+        mock_resp.status = 200
+        mock_resp.__aenter__ = AsyncMock(return_value=mock_resp)
+        mock_resp.__aexit__ = AsyncMock(return_value=False)
+
+        with patch("aiohttp.ClientSession.post", return_value=mock_resp):
+            await client.notify_market_open("Korea")
+            # Session should be created
+            assert client._session is not None
+
+            session1 = client._session
+            await client.notify_market_close("Korea", 1.5)
+            # Same session should be reused
+            assert client._session is session1
+
+
+class TestRateLimiting:
+    """Test rate limiter behavior."""
+
+    @pytest.mark.asyncio
+    async def test_rate_limiter_enforced(self) -> None:
+        """Rate limiter delays rapid requests."""
+        import time
+
+        client = TelegramClient(
+            bot_token="123:abc", chat_id="456", enabled=True, rate_limit=2.0
+        )
+
+        mock_resp = AsyncMock()
+        mock_resp.status = 200
+        mock_resp.__aenter__ = AsyncMock(return_value=mock_resp)
+        mock_resp.__aexit__ = AsyncMock(return_value=False)
+
+        with patch("aiohttp.ClientSession.post", return_value=mock_resp):
+            start = time.monotonic()
+
+            # Send 3 messages (rate: 2/sec = 0.5s per message)
+            await client.notify_market_open("Korea")
+            await client.notify_market_open("United States")
+            await client.notify_market_open("Japan")
+
+            elapsed = time.monotonic() - start
+
+            # Should take at least 0.4 seconds (3 msgs at 2/sec with some tolerance)
+            assert elapsed >= 0.4
+
+
+class TestMessagePriorities:
+    """Test priority-based messaging."""
+
+    @pytest.mark.asyncio
+    async def test_low_priority_uses_info_emoji(self) -> None:
+        """LOW priority uses ℹ️ emoji."""
+        client = TelegramClient(
+            bot_token="123:abc", chat_id="456", enabled=True
+        )
+
+        mock_resp = AsyncMock()
+        mock_resp.status = 200
+        mock_resp.__aenter__ = AsyncMock(return_value=mock_resp)
+        mock_resp.__aexit__ = AsyncMock(return_value=False)
+
+        with patch("aiohttp.ClientSession.post", return_value=mock_resp) as mock_post:
+            await client.notify_market_open("Korea")
+
+            payload = mock_post.call_args.kwargs["json"]
+            assert NotificationPriority.LOW.emoji in payload["text"]
+
+    @pytest.mark.asyncio
+    async def test_critical_priority_uses_alarm_emoji(self) -> None:
+        """CRITICAL priority uses 🚨 emoji."""
+        client = TelegramClient(
+            bot_token="123:abc", chat_id="456", enabled=True
+        )
+
+        mock_resp = AsyncMock()
+        mock_resp.status = 200
+        mock_resp.__aenter__ = AsyncMock(return_value=mock_resp)
+        mock_resp.__aexit__ = AsyncMock(return_value=False)
+
+        with patch("aiohttp.ClientSession.post", return_value=mock_resp) as mock_post:
+            await client.notify_system_shutdown("Circuit breaker tripped")
+
+            payload = mock_post.call_args.kwargs["json"]
+            assert NotificationPriority.CRITICAL.emoji in payload["text"]
+
+
+class TestClientCleanup:
+    """Test client cleanup behavior."""
+
+    @pytest.mark.asyncio
+    async def test_close_closes_session(self) -> None:
+        """close() closes the HTTP session."""
+        client = TelegramClient(
+            bot_token="123:abc", chat_id="456", enabled=True
+        )
+
+        mock_session = AsyncMock()
+        mock_session.closed = False
+        mock_session.close = AsyncMock()
+        client._session = mock_session
+
+        await client.close()
+        mock_session.close.assert_called_once()
+
+    @pytest.mark.asyncio
+    async def test_close_handles_no_session(self) -> None:
+        """close() handles None session gracefully."""
+        client = TelegramClient(
+            bot_token="123:abc", chat_id="456", enabled=True
+        )
+
+        # Should not raise exception
+        await client.close()