refactor: optimize startup, improve security, and simplify n8n configuration for v2 compatibility

fix: remove N8N_ENCRYPTION_KEY from Duplicate Space secrets (auto-generated by n8n)

feat: add secrets definition to HF Space frontmatter for Duplicate Space dialog

feat: add open-source files, fix critical bugs, rewrite README with Duplicate Space button

fix: use valid emoji for HF metadata

initial commit