v1.0.0: remove.bg migration kit

First release of the remove.bg → PixMiller migration kit.

• Docs (English + 简体中文): getting started, full migration reference, client libraries, production checklist, FAQ
• Tested examples: curl, Python, Node.js, PHP, Go, Ruby, Java
• Scripts: find-removebg-usages, verify-key, smoke-test
• Agent skill remove-bg-migration (Claude Code plugin / npx skills add PixMiller/remove-bg-migration)

Videos (attached below, © Ullr AI Lab):

• removebg-api-en.mp4: API migration for developers (60 s)
• removebg-api-zh.mp4: API 迁移（中文，53 秒）
• removebg-web-en.mp4: switching from the remove.bg website (38 s)
• batch-switch-en.mp4: batch background removal (28 s)