feat: implement logging service with file output

- setup_logging() creates logs/ dir and writes timestamped log file
- format: asctime name levelname message
- falls back to console-only if log dir is not writable
- main.py now calls setup_logging() at startup and logs app name/version

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

src/main.py

@@ -1,18 +1,26 @@
+import logging
 import sys
 
 from PySide6.QtWidgets import QApplication
 
 from app.main_window import MainWindow
-from version import APP_NAME
+from services.log_service import setup_logging
+from version import APP_NAME, APP_VERSION
+
+logger = logging.getLogger(__name__)
 
 
 def main():
+    setup_logging()
+    logger.info("Application starting: %s %s", APP_NAME, APP_VERSION)
+
     app = QApplication(sys.argv)
     app.setApplicationName(APP_NAME)
 
     window = MainWindow()
     window.show()
 
+    logger.info("Main window displayed")
     return app.exec()
 
 

src/services/log_service.py

@@ -1,8 +1,45 @@
 import logging
+import os
+from datetime import datetime
 
 
-def setup_logging():
-    logging.basicConfig(
-        level=logging.INFO,
-        format="%(asctime)s - %(name)s - %(levelname)s - %(message)s",
-    )
+def setup_logging(log_dir=None):
+    """Initialize file + console logging. Call once at application startup.
+
+    log_dir: absolute path to log directory. Defaults to <project_root>/logs/.
+    If the directory cannot be created, falls back to console-only logging.
+    """
+    if log_dir is None:
+        # src/services/log_service.py -> src/services -> src -> project root
+        _here = os.path.dirname(os.path.abspath(__file__))
+        log_dir = os.path.join(os.path.dirname(os.path.dirname(_here)), "logs")
+
+    try:
+        os.makedirs(log_dir, exist_ok=True)
+    except OSError as exc:
+        logging.basicConfig(
+            level=logging.INFO,
+            format="%(asctime)s %(name)s %(levelname)s %(message)s",
+        )
+        logging.getLogger(__name__).warning(
+            "Cannot create log directory %s: %s. Falling back to console only.", log_dir, exc
+        )
+        return
+
+    timestamp = datetime.now().strftime("%Y%m%d_%H%M%S")
+    log_file = os.path.join(log_dir, "app_{}.log".format(timestamp))
+
+    formatter = logging.Formatter("%(asctime)s %(name)s %(levelname)s %(message)s")
+
+    root = logging.getLogger()
+    root.setLevel(logging.INFO)
+
+    fh = logging.FileHandler(log_file, encoding="utf-8")
+    fh.setFormatter(formatter)
+    root.addHandler(fh)
+
+    sh = logging.StreamHandler()
+    sh.setFormatter(formatter)
+    root.addHandler(sh)
+
+    logging.getLogger(__name__).info("Logging initialized. Log file: %s", log_file)