docs: remove PM2/bare-metal references

docs/BACKEND_ARCHITECTURE.md

@@ -42,7 +42,6 @@ backend/
 │ │ ├── room.ts
 │ │ └── socket.ts
 │ └── server.ts     # Main application entry point: Express and Socket.IO setup
-├── ecosystem.config.js # PM2 configuration file
 ├── package.json
 └── tsconfig.json
 ```
@@ -132,4 +131,4 @@ Redis is a key component of the backend, used to store all temporary state. We c
   - **Purpose**: Tracks the number of visits from different sources (Referrers) on a daily basis.
   - **Fields**: The referrer's domain name (e.g., `google.com`, `github.com`).
   - **Value**: The cumulative visit count for the day.
-  - **Logic**: The `HINCRBY` command is used to atomically increment the count for a specified source. 
+  - **Logic**: The `HINCRBY` command is used to atomically increment the count for a specified source. 

docs/BACKEND_ARCHITECTURE.zh-CN.md

@@ -42,7 +42,6 @@ backend/
 │ │ ├── room.ts
 │ │ └── socket.ts
 │ └── server.ts # 主应用程序入口点: Express 和 Socket.IO 设置
-├── ecosystem.config.js # PM2 配置文件
 ├── package.json
 └── tsconfig.json
 ```