Fix CI: add httpx for backend tests, upgrade Node to 20 for frontend build

Added httpx to backend dependencies and updated Node.js version to 20.

Author: DHANUSHGCODE

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
       - name: Install backend deps
         run: |
           pip install -r backend/requirements.txt
-          pip install pytest pytest-cov
+          pip install pytest pytest-cov httpx
       - name: Run backend tests
         run: |
           cd backend
@@ -27,7 +27,7 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
         with:
-          node-version: '18'
+          node-version: '20'
       - name: Install frontend deps
         run: |
           cd frontend