pydlock v2.0.6

Branding and packaging-metadata polish — no code changes.

• Project logo. Added a brand mark — a padlock formed by an ouroboros
  serpent (Python + padlock + a sealed loop) — under brand/: a light/dark
  README lockup (<picture> theme-swap), the mark tile, and black/white
  transparent mono variants. The wordmark uses Sora (SIL OFL 1.1), vendored
  with its full license.

• Docs logo. The Read the Docs sidebar now shows the mark (furo
  light/dark logo).

• Project URLs. Standardized the PyPI project links: Documentation
  now points at the released docs (/en/stable/ rather than /en/latest/),
  added a Changelog link to the GitHub releases, and renamed Bug Tracker
  to Issues.