feat(dify): add EverOS Cloud memory plugin

[Yangtze-Seventh]

Summary

• add a separate evermind-ai/everos_cloud Dify tool plugin for EverOS Cloud
• provide cloud credential setup with the production API URL and a workspace-owned API key
• add persistent memory search and write/flush tools with Dify-controlled user, app, and session isolation
• document deployment, privacy, security boundaries, and English/Chinese usage
• add locked dependencies and CI packaging verification

Validation

• 83 passed
• Ruff lint passed
• Dify CLI v0.6.10 package validation passed
• packaged requirements match uv.lock
• archive integrity check passed
• secret scan found no credentials
• end-to-end local Dify test passed against EverOS Cloud: add, flush, delayed search, Chinese, English/Unicode, and memory update cases