fix: use venv pip to avoid externally-managed-environment error

start_server.sh

@@ -32,7 +32,7 @@ source .venv/bin/activate
 
 # 3. Check and Install Backend Dependencies
 echo "📦 Updating Python dependencies..."
-pip install -r backend/requirements.txt
+.venv/bin/pip install -r backend/requirements.txt
 
 # 4. Get Local IP and set environment variables
 LOCAL_IP=$(hostname -I | awk '{print $1}' || echo "localhost")