Add Mintlify documentation site

[sidmohan0]

Summary

• add a Mintlify site under docs/ for DataFog Core
• document installation, quickstarts, findings, ranges, transformations, configuration, pseudonymization, and tokenization
• add Rust, Python, Node.js, browser/WASM, and error references
• exclude internal ADR and migration documents from the public Mintlify build
• distinguish datafog-core from the established datafog Python package and mark pending npm releases accurately

Verification

• mint validate
• mint broken-links --check-anchors
• git diff --check