ci: add workflow for build process

.github/workflows/build.yaml

@@ -0,0 +1,51 @@
+name: MERN-Auth | Build
+
+on:
+  pull_request:
+    branches:
+      - develop
+  workflow_dispatch:
+
+jobs:
+  build:
+    name: Build Application
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout Code
+        uses: actions/checkout@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: 18
+
+      - name: Cache Node Modules
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.npm
+            node_modules
+            frontend/node_modules
+          key: ${{ runner.os }}-node-${{ hashFiles('**/package-lock.json', '**/frontend/package-lock.json') }}
+          restore-keys: |
+            ${{ runner.os }}-node-
+
+      - name: Install Backend Dependencies
+        run: npm ci --cache .npm --prefer-offline
+
+      - name: Run Backend Build
+        env:
+          MONGO_URI: ${{ secrets.MONGO_URI }}
+          JWT_SECRET: ${{ secrets.JWT_SECRET }}
+          EMAILJS_SERVICE_ID: ${{ secrets.EMAILJS_SERVICE_ID }}
+          EMAILJS_TEMPLATE_ID: ${{ secrets.EMAILJS_TEMPLATE_ID }}
+          EMAILJS_PUBLIC_KEY: ${{ secrets.EMAILJS_PUBLIC_KEY }}
+          EMAILJS_PRIVATE_KEY: ${{ secrets.EMAILJS_PRIVATE_KEY }}
+        run: npm run build
+
+      - name: Install Frontend Dependencies
+        run: npm ci --cache .npm --prefer-offline --prefix frontend
+
+      - name: Run Frontend Build
+        run: npm run build --prefix frontend