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/application.py

@@ -0,0 +1,43 @@
+"""
+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.
+"""
+
+from fastapi import FastAPI
+from app.core.error_handlers import install_error_handlers
+from app.core.logger import get_logger
+
+logger = get_logger(__name__)
+
+# Create FastAPI app instance
+app = FastAPI(
+    title="ChatterMate API",
+    description="AI-Powered Customer Support Platform",
+    version="1.0.0"
+)
+
+# 5xx bodies must not carry our own error text; see error_handlers.
+install_error_handlers(app)
+
+def initialize_cors_listener():
+    """
+    Initialize the CORS listener for multi-worker environments
+    This function is called during application startup
+    """
+    try:
+        from app.core.cors import start_cors_listener
+        start_cors_listener(app)
+        logger.info("CORS listener initialized")
+    except Exception as e:
+        logger.error(f"Failed to initialize CORS listener: {str(e)}")