feat: add interactive prompt for main/dev branch choice

update-Nitrov3.sh

@@ -22,6 +22,17 @@ if [ -z "${NITRO_SITE_URL:-}" ]; then
     export NITRO_SITE_URL
 fi
 
+# Prompt for branch if not set in .env
+if [ -z "${NITRO_BRANCH:-}" ]; then
+    read -r -p "Enter branch to use (main/dev) [main]: " NITRO_BRANCH
+    NITRO_BRANCH="${NITRO_BRANCH:-main}"
+    if [ "$NITRO_BRANCH" != "main" ] && [ "$NITRO_BRANCH" != "dev" ]; then
+        echo "=== ❌ Invalid branch '$NITRO_BRANCH'. Choose 'main' or 'dev'. ==="
+        exit 1
+    fi
+    export NITRO_BRANCH
+fi
+
 # Real-time output via pseudo-terminal (unbuffer from expect)
 if [ -z "${_UNBUFFERED:-}" ] && command -v unbuffer &> /dev/null; then
     export _UNBUFFERED=1