Add project documentation (README.md)

README.md

+# Project 2: Distributed gRPC Calculator
+
+This project is a distributed numerical calculator system (addition and multiplication) built with gRPC. It features services written in different languages (Python, Go, and Java) that communicate with each other.
+
+## Project Structure
+
+* `/proto`: Contains the unified `.proto` contract file (`calculator.proto`).
+* `/addition_service`: The Addition Service, written in **Python**.
+* `/multiplication_service`: The Multiplication Service, written in **Go**.
+* `/src/main/java`: The Client Gateway, written in **Java**.
+* `README.md`: This documentation file.
+
+##  How to Run the Project
+
+To run the full project, you must run all 3 components in **3 separate Terminal windows**, in order.
+
+### 1. Run the Addition Service (Python)
+
+1.  Open a Terminal.
+2.  Navigate to the service directory:
+    ```bash
+    cd addition_service
+    ```
+3.  (First time only) Install dependencies:
+    ```bash
+    pip install grpcio grpcio-tools
+    ```
+4.  Run the server (it will keep running on port `50051`):
+    ```bash
+    python server.py
+    ```
+    * *Expected output: `Addition Service server started on port 50051...`*
+
+### 2. Run the Multiplication Service (Go)
+
+1.  Open a **new, separate** Terminal.
+2.  Navigate to the service directory:
+    ```bash
+    cd multiplication_service
+    ```
+3.  (First time only) Download dependencies:
+    ```bash
+    go mod tidy
+    ```
+4.  Run the server (it will keep running on port `50052`):
+    ```bash
+    go run server.go
+    ```
+    * *Expected output: `Multiplication Service server started on port 50052...`*
+
+### 3. Run the Java Gateway (Client)
+
+1.  Ensure both the Python and Go servers are running in their terminals.
+2.  Open the project in IntelliJ IDEA.
+3.  Open the `ClientGateway.java` file located at:
+    `src/main/java/com/example/grpc/calculator/ClientGateway.java`
+4.  Right-click anywhere in the code and select **"Run 'ClientGateway.main()'"**.
+
+##  Example Input/Output
+
+Once the Java client is running, it will become interactive in the "Run" console window.
+
+1.  **Input (Option 1):**
+    ```
+    Enter your choice: 1
+    Enter number 1: 10
+    Enter number 2: 5
+    ```
+2.  **Output (The Result):**
+    ```
+    Calling services with num1=10, num2=5
+    Addition Result (from Python): 15
+    Multiplication Result (from Go): 50
+    ```
+
+---
+
+1.  **Input (Option 2):**
+    ```
+    Enter your choice: 2
+    ```
+2.  **Output (The Streaming Log):**
+    ```
+    --- Fetching Addition Log (Python) ---
+    Add Operation: 10 + 5 = 15
+    
+    --- Fetching Multiplication Log (Go) ---
+    Multiply Operation: 10 * 5 = 50
+    ```
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