fix(dify): prepare EverOS Self-Hosted for Marketplace

[Yangtze-Seventh]

Summary

• rename the plugin to EverOS Self-Hosted / EverOS 本地版
• replace the previous icon with the new EverOS brand mark
• normalize the Marketplace author identifier to lowercase evermind-ai
• clarify that the provider URL points to a self-hosted EverOS deployment
• add the public support contact contact@evermind.ai

Verification

• uv run ruff check .
• uv lock --check
• uv run pytest — 82 passed
• Dify CLI package generation succeeded
• packaged runtime requirements exactly match the frozen uv.lock export
• ZIP integrity check passed
• basic secret-pattern scan found no credentials

Notes

The generated .difypkg is intentionally not committed to this source repository. A fresh package will be generated from the merged source for the separate Dify Marketplace submission.