Add code to run npm start in both client & server

- Created a `run.js` script to automate the execution of `npm start` in both `client` and `server` directories.
- Added a check for `node_modules` to run `npm install` if missing before starting the applications.
- Updated root `package.json` with `install-all` and `start-all` scripts for easy installation and starting of both client and server simultaneously.

run.js

@@ -0,0 +1,27 @@
+const { spawn } = require('child_process');
+const path = require('path');
+const fs = require('fs');
+
+const directories = ['client', 'server'];
+
+function runCommand(command, args, cwd) {
+    const proc = spawn(command, args, { cwd, stdio: 'inherit', shell: true });
+    proc.on('close', (code) => {
+        if (code !== 0) {
+            console.error(`Process in ${cwd} exited with code ${code}`);
+        }
+    });
+}
+
+directories.forEach(dir => {
+    const fullPath = path.join(__dirname, dir);
+
+    // Check if node_modules exists; if not, run npm install first
+    if (!fs.existsSync(path.join(fullPath, 'node_modules'))) {
+        console.log(`node_modules not found in ${dir}. Running npm install...`);
+        runCommand('npm', ['install'], fullPath);
+    }
+
+    console.log(`Starting npm start in ${dir}`);
+    runCommand('npm', ['start'], fullPath);
+});