Add file logging: write daily logs to logs/ directory

Uses TimedRotatingFileHandler with 30-day retention. Logs to both
console and logs/telegram_YYYYMMDD.log automatically on startup.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

testing_telegram_bot.py

@@ -19,6 +19,7 @@ Usage:
 
 import asyncio
 import logging
+import logging.handlers
 import os
 import signal
 import sys
@@ -49,11 +50,19 @@ from pair_signals import produce_signal
 if hasattr(sys.stdout, "reconfigure"):
     sys.stdout.reconfigure(encoding="utf-8")
 
-logging.basicConfig(
-    format="%(asctime)s [%(levelname)s] %(name)s: %(message)s",
-    level=logging.INFO,
-    datefmt="%H:%M:%S",
+_LOG_DIR = os.path.join(os.path.dirname(os.path.abspath(__file__)), "logs")
+os.makedirs(_LOG_DIR, exist_ok=True)
+_log_file = os.path.join(_LOG_DIR, f"telegram_{datetime.now().strftime('%Y%m%d')}.log")
+
+_fmt = logging.Formatter("%(asctime)s [%(levelname)s] %(name)s: %(message)s", datefmt="%H:%M:%S")
+_console = logging.StreamHandler()
+_console.setFormatter(_fmt)
+_file_handler = logging.handlers.TimedRotatingFileHandler(
+    _log_file, when="midnight", backupCount=30, encoding="utf-8",
 )
+_file_handler.setFormatter(_fmt)
+
+logging.basicConfig(level=logging.INFO, handlers=[_console, _file_handler])
 logging.getLogger("httpx").setLevel(logging.WARNING)
 logging.getLogger("httpcore").setLevel(logging.WARNING)
 logger = logging.getLogger("telegram_bot")