📦 添加虚拟环境和启动脚本

新增:
- backend/venv/ - Python 虚拟环境
- backend/start.sh - 启动脚本（使用虚拟环境）
- backend/requirements.txt - 依赖列表
- .gitignore - 忽略虚拟环境和缓存文件

说明:
- 每个项目使用独立虚拟环境
- 避免依赖冲突
- 启动脚本自动创建和激活虚拟环境

frontend/node_modules/webpack/schemas/plugins/optimize/AggressiveSplittingPlugin.json

@@ -0,0 +1,23 @@
+{
+  "title": "AggressiveSplittingPluginOptions",
+  "type": "object",
+  "additionalProperties": false,
+  "properties": {
+    "chunkOverhead": {
+      "description": "Extra cost for each chunk (Default: 9.8kiB).",
+      "type": "number"
+    },
+    "entryChunkMultiplicator": {
+      "description": "Extra cost multiplicator for entry chunks (Default: 10).",
+      "type": "number"
+    },
+    "maxSize": {
+      "description": "Byte, max size of per file (Default: 50kiB).",
+      "type": "number"
+    },
+    "minSize": {
+      "description": "Byte, split point. (Default: 30kiB).",
+      "type": "number"
+    }
+  }
+}