fix: install backend Node.js deps (ws) in start scripts

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

start.bat

@@ -58,6 +58,9 @@ if %errorlevel% neq 0 (
     exit /b 1
 )
 echo [*] Backend dependencies OK.
+echo [*] Installing backend Node.js dependencies...
+call npm install --silent
+echo [*] Backend Node.js dependencies OK.
 cd ..
 
 echo.

start.sh

@@ -52,6 +52,9 @@ if [ $? -ne 0 ]; then
 fi
 echo "[*] Backend dependencies OK."
 deactivate
+echo "[*] Installing backend Node.js dependencies..."
+npm install --silent
+echo "[*] Backend Node.js dependencies OK."
 
 cd "$SCRIPT_DIR"