docs(conduct): adopt the Contributor Covenant, with a stance on religious disagreement

[eaitbrahim]

Closes #284

A project inviting international contributors around a religious topic needs a stated
behavioural baseline before it needs anything else.

What

• CODE_OF_CONDUCT.md: canonical Contributor Covenant text fetched from GitHub's
  codes-of-conduct API (the same trusted-source trick as the Apache-2.0 LICENSE in chore(license): add Apache-2.0 and declare it in all six distributions #296 —
  not retyped), with the [INSERT CONTACT METHOD] placeholder filled with the maintainer's
  address.
• One project-specific addition, appended as its own section:
  • disagreement about a religious ruling is expected and legitimate — not disloyalty,
    not trolling, not a conduct problem;
  • disparaging a madhhab, a school, a scholar, or a contributor's own practice is not —
    enforced exactly like any other harassment ("the Hanafi position on X is wrong" is an
    argument; "nobody serious follows that" is an attack);
  • the technical route for disagreement is a local attestation (keel assets attest) or
    the Compliance & classification Discussions category — never a pull-request thread, and
    never a remark about the person holding the other view.

Tests (tests/test_code_of_conduct.py, red first): all five Covenant section headings
present (the file is the Covenant, not a bespoke policy); no [INSERT placeholder survives
(the unfilled-template failure shape); a concrete reachable contact is named; and the
religious-disagreement stance exists with its three required elements (madhhab line,
expected-and-legitimate, local-attestation route).

Gates: pytest 2,798 passed / 1 skipped, ruff check clean, mypy clean.