refactor: fix reverse dependencies — logger_manager→utils, dashboard_service extraction

- Move SystemLogger implementation to utils/logger_manager.py (pure utility, no deps)
- services/logger_manager.py becomes a backward-compat re-export shim
- database/manager.py and database/vendor_manager.py now import from utils layer
- Extract get_dashboard_stats() to services/dashboard_service.py
- services/task_runner.py no longer imports from routes layer
- routes/dashboard_routes.py get_dashboard_stats() delegates to service layer

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

utils/logger_manager.py

@@ -0,0 +1,53 @@
+import logging
+import os
+import sys
+from logging.handlers import RotatingFileHandler
+
+class SystemLogger:
+    """
+    自定義系統日誌管理器
+    封裝 logging 模組，提供統一的日誌格式與輸出設定 (Console + File)
+    """
+    def __init__(self, name="System", log_file='system.log'):
+        self.logger = logging.getLogger(name)
+        self.logger.setLevel(logging.DEBUG)
+
+        # 避免重複添加 Handler (防止日誌重複輸出)
+        if not self.logger.handlers:
+            # 取得專案根目錄 (假設此檔案位於 utils/ 目錄下，往上兩層為根目錄)
+            base_dir = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
+            log_dir = os.path.join(base_dir, 'logs')
+
+            # 確保 logs 目錄存在
+            if not os.path.exists(log_dir):
+                try:
+                    os.makedirs(log_dir)
+                except OSError:
+                    pass # 忽略無法建立目錄的錯誤，改由 Console 輸出
+
+            file_path = os.path.join(log_dir, log_file)
+
+            # 1. 檔案輸出 (RotatingFileHandler) - 支援自動切割
+            try:
+                file_handler = RotatingFileHandler(
+                    file_path,
+                    maxBytes=10*1024*1024, # 10MB 切割
+                    backupCount=5,
+                    encoding='utf-8'
+                )
+                file_handler.setLevel(logging.DEBUG)
+                formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
+                file_handler.setFormatter(formatter)
+                self.logger.addHandler(file_handler)
+            except Exception as e:
+                print(f"⚠️ Logger Init Warning: 無法建立日誌檔案 ({e})")
+
+            # 2. 控制台輸出 (StreamHandler)
+            console_handler = logging.StreamHandler(sys.stdout)
+            console_handler.setLevel(logging.INFO)
+            console_formatter = logging.Formatter('%(asctime)s - %(levelname)s - %(message)s')
+            console_handler.setFormatter(console_formatter)
+            self.logger.addHandler(console_handler)
+
+    def get_logger(self):
+        return self.logger