Fix scripts for Next.js + Payload CMS workflow

- new-project.sh: Use nextjs-payload-starter template, Next.js AI rules
- convert-astro.sh: Complete rewrite to migrate Astro MDX to Payload CMS Lexical JSON
- deploy.sh: Check for next.config instead of astro.config.mjs, use MONGODB_URL
- preview.sh: Check for Next.js, default port 3002
- audit-seo.sh: Check .tsx pages in src/app, Next.js config

All scripts now properly support Next.js + Payload CMS workflow.

skills/website-creator/scripts/preview.sh

@@ -19,7 +19,7 @@ NC='\033[0m'
 
 # Default values
 PROJECT_PATH="${1:-.}"
-PORT="${2:-4321}"
+PORT="${2:-3002}"
 HOST="0.0.0.0"
 
 #-------------------------------------------------------------------------------
@@ -64,13 +64,13 @@ check_project() {
         exit 1
     fi
     
-    # Check for Astro or Emdash
-    if ! grep -q "astro" "$PROJECT_PATH/package.json"; then
-        log_error "ไม่ใช่ Astro project"
+    # Check for Next.js
+    if ! grep -q '"next"' "$PROJECT_PATH/package.json"; then
+        log_error "ไม่ใช่ Next.js project"
         exit 1
     fi
-    
-    log_success "พบ Astro project"
+
+    log_success "พบ Next.js project"
 }
 
 #-------------------------------------------------------------------------------
@@ -159,7 +159,7 @@ check_port() {
 
 main() {
     echo "=============================================="
-    echo "  Astro Preview Server"
+    echo "  Next.js Preview Server"
     echo "=============================================="
     echo ""