build: 打通 FastAPI 与 Vue 最小工程、依赖与数据库连接

后端入口、配置、Redis 与 Alembic 迁移就位；前端 Vite 工程可安装可构建。

backend/app/core/logger.py

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+"""
+Copyright 2024-2026 ChatterMate
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+"""
+
+import logging
+import sys
+from logging.handlers import RotatingFileHandler
+import os
+
+# Dictionary to store loggers by name
+_loggers = {}
+
+
+def get_logger(name=None):
+    """
+    Get or create a logger instance.
+    Args:
+        name: The name for the logger (typically __name__ from the calling module)
+    Returns:
+        A configured logger instance
+    """
+    # Use the provided name or default to 'app'
+    logger_name = name or 'app'
+
+    # Return existing logger if already created
+    if logger_name in _loggers:
+        return _loggers[logger_name]
+
+    # Create new logger
+    logger = logging.getLogger(logger_name)
+
+    # Only set up handlers if they haven't been set up already
+    if not logger.handlers:
+        logger.setLevel(logging.DEBUG)
+
+        # Create formatters and handlers
+        formatter = logging.Formatter(
+            '%(asctime)s - %(name)s - %(levelname)s - %(message)s'
+        )
+
+        # Console handler
+        console_handler = logging.StreamHandler(sys.stdout)
+        console_handler.setFormatter(formatter)
+        logger.addHandler(console_handler)
+
+        # File handler
+        log_dir = 'logs'
+        if not os.path.exists(log_dir):
+            os.makedirs(log_dir)
+
+        file_handler = RotatingFileHandler(
+            f'{log_dir}/app.log',
+            maxBytes=10485760,  # 10MB
+            backupCount=5
+        )
+        file_handler.setFormatter(formatter)
+        logger.addHandler(file_handler)
+
+    # Store logger in dictionary
+    _loggers[logger_name] = logger
+    return logger