update local startup flow and add root env example

Make the project start more reliably in the current Windows bash setup, add a safe root .env.example for onboarding, and lower the backend Python floor to 3.11 to match the validated local environment.

start.sh

@@ -267,9 +267,16 @@ fi
 BACKEND_PID="$!"
 
 echo "Waiting for backend..."
-sleep 5
+backend_ready=false
+for _ in $(seq 1 30); do
+  if port_in_use "$BACKEND_PORT"; then
+    backend_ready=true
+    break
+  fi
+  sleep 1
+done
 
-if ! port_in_use "$BACKEND_PORT"; then
+if [[ "$backend_ready" != true ]]; then
   echo "[ERROR] Backend did not start successfully."
   echo "[ERROR] Check logs: $BACKEND_LOG $BACKEND_ERR_LOG"
   exit 1
@@ -283,7 +290,7 @@ echo "Starting frontend on port ${FRONTEND_PORT}..."
 if [[ "$USE_WINDOWS_TOOLS" == true ]]; then
   (
     cd "$FRONTEND_DIR"
-    exec cmd.exe /c npm run dev -- --host "$FRONTEND_HOST"
+    exec cmd.exe /c npm.cmd run dev -- --host "$FRONTEND_HOST"
   ) >"$FRONTEND_LOG" 2>"$FRONTEND_ERR_LOG" &
   FRONTEND_PID="$!"
 else