fix: Support random password generation on initial WordPress install

- Allow empty WP_ADMIN_PASSWORD on initial install for backward compatibility
- Generate secure random password (20 chars) when password is not specified
- During Helm upgrades: Skip installation (WordPress already installed)
- Prevents password mismatch between Kubernetes Secret and WordPress database

Changes:
- Use INSTALL_PASSWORD variable for flexible password handling
- Generate random password with: openssl rand -base64 32 | tr -d "=+/" | cut -c1-20
- Improve logging to distinguish between random generation and manual specification
- Preserve existing database content during upgrades (no password reset)

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

templates/deployment.yaml

@@ -145,10 +145,12 @@ spec:
               if [ -z "$TABLES" ]; then
                 echo "=== Starting WordPress Installation ==="
 
-                if [ -z "$WP_ADMIN_PASSWORD" ]; then
-                  echo "ERROR: WP_ADMIN_PASSWORD is not set. WordPress installation requires an admin password."
-                  echo "Skipping WordPress installation. Please set WP_ADMIN_PASSWORD in values.yaml"
-                  exit 1
+                # 初回インストール時のパスワード処理
+                INSTALL_PASSWORD="$WP_ADMIN_PASSWORD"
+                if [ -z "$INSTALL_PASSWORD" ]; then
+                  # パスワードが空の場合は、ランダムに生成する
+                  INSTALL_PASSWORD=$(openssl rand -base64 32 | tr -d "=+/" | cut -c1-20)
+                  echo "INFO: WP_ADMIN_PASSWORD is not set. Generated random password."
                 fi
 
                 INSTALL_URL="http://127.0.0.1"
@@ -158,13 +160,17 @@ spec:
                   --url="$INSTALL_URL" \
                   --title="$WP_SITE_TITLE" \
                   --admin_user="$WP_ADMIN_USER" \
-                  --admin_password="$WP_ADMIN_PASSWORD" \
+                  --admin_password="$INSTALL_PASSWORD" \
                   --admin_email="$WP_ADMIN_EMAIL" \
                   --skip-email
 
                 echo "=== WordPress Installation Completed ==="
                 echo "Admin User: $WP_ADMIN_USER"
-                echo "Admin password was set from values.yaml"
+                if [ -z "$WP_ADMIN_PASSWORD" ]; then
+                  echo "INFO: Generated admin password. Check Secret for details."
+                else
+                  echo "Admin password was set from values.yaml"
+                fi
               else
                 echo "WordPress is already installed, skipping installation"
                 if [ -f /tmp/wp-cli.phar ]; then