chore: update default port from 3003 to 3000 and improve installation docs

- Change all default port references from 3003 to 3000 across scripts and documentation
- Add quick installation guide for batch plugin installation to main README (EN & CN)
- Simplify installation options by removing manual installation instructions
- Update deployment guides and examples to reflect new default port

scripts/.env.example

@@ -0,0 +1,20 @@
+# OpenWebUI Bulk Installer Configuration
+# 
+# Instructions:
+# - api_key: Copy from OpenWebUI Settings (starts with sk-)
+# - url: OpenWebUI server address
+#
+# Environment variable precedence (highest to lowest):
+# 1. OPENWEBUI_API_KEY / OPENWEBUI_URL environment variables
+# 2. OPENWEBUI_BASE_URL environment variable
+# 3. Configuration in this .env file
+
+# API Key (required)
+api_key=sk-your-api-key-here
+
+# OpenWebUI server address (required)
+url=http://localhost:3000
+
+# Alternatively, use environment variable format (both methods are equivalent)
+# OPENWEBUI_API_KEY=sk-your-api-key-here
+# OPENWEBUI_BASE_URL=http://localhost:3000